I have question, why is my Edit mode rig setup is diffrent than pose mode rig look?

Ok rred-izak I had a quick look. In edit mode you have some bones hidden. Press ALT + H to unhide them. The position of the bones is different in edit mode because of the action constraint, the influence is all the way up at 1. Lower to 0 and they will be back at there original position. If you are following the tutorial step by step check the setting in the tutorial compared to yours if you are using a different version of Blender as the default setting may have changed.

I hope this solves your problem.

rred-izak The "Pose Mode" is where you add the various "Bone Constraints" which therefore only have an effect on the bones when being in that mode. That's why you often  see at least some slight movement of the bones when switching from "Edit Mode" to "Pose Mode".

Hello, yes, it was the frame when it comes to crest. Blender decided to use minus -20 even if i selected 1st one? i dunno why. I have no idea why but it works.

I have no idea though what causes shift in the spine and wings, i have no action constraints there

Thanks for your help!

@Ingmar Franz so it's ok for it to happen?

rred-izak  Yes, the "Bone Constraints" start working as soon as you switch to "Pose Mode" unless 

1) you set a constraint's influence to zero or

2) turn it off (by clicking the eye symbol in the constraint's header so that it looks closed) or 

3) set your armature to "Rest Position" (in  the "Skeleton" panel of the armature's "Object Data Properties" tab).

Let's look for example at the bone "DEF_fthrFlightB.000" in Piero's left wing (see image below, yellow frame). It copies its rotation mainly from bone "DEF_fthrFlightA.000" ( "Copy Rotation" constraint with an influence of 1) and with a reduced influence of 0.333 from DEF_fthrFlightD.000. As soon as you switch from "Edit Mode" to "Pose Mode", DEF_fthrFlightA.000 and DEF_fthrFlightD.000 start pulling DEF_fthrFlightB.000 into their directions:

 And this causes the snapping of all "Deformation Bones" in between the "Feather Control Bones" CTRL_fthrFlight.000 to CTRL_fthrFlight.003 (the large bones hanging down from the wing "arm").

All "Bone Constraints" that copy transformations from other bones can act like this.

The "Crown Feathers" of your Piero are influenced by the rotation of "DEF_head.002" around its local X axis (Note: "DEF_head.002"should be renamed properly as "CTRL_crown" as well as some other bones in the head (see my rig here)). This bone is in your file rotated 0 degrees around its local X axis. The "Copy Rotation" constraint maps 

1) a rotation of -45 degrees of your "DEF_head.002" bone to frame 1 of the "MCH_crownSpread" action ("Crown Feathers" bend backwards to their extreme position) and 

2) a rotation of 45 degrees of your "DEF_head.002" bone to frame 20 of the "MCH_crownSpread" action ("Crown Feathers" bend forwards to their extreme position) 

This means that  "DEF_head.002" in its default position of 0 degrees rotation aroung its local X axis is mapped to a "Crown Feathers" spread in the middle between these two extremes mentioned above. This position isn't identical with the "Rest Position" of the "Crown Feather Deformation Bones" in "Edit Mode" so that these bones are spread forwards when switching from "Edit Mode" to "Pose Mode".

By the way: The frame numbers for the action adressed in your "Copy Action" constraint must be positive! See the Blender 2.93 Manual here:

Frame Start, End

The starting and ending frames of the action to be mapped.

Note

• These values must be strictly positive.

• By default, both values are set to 0, which disables the mapping (i.e. the owner just gets the properties defined at frame 0 of the linked action…).

Hello again and thanks for your great explanation, means a lot! Now I can say i understand these dependencies.

I'm a total beginner and seriously it's my first rig ever, I decided to simplyfy wing and give it ik arm and rotation constraints between feathers. I saw many mistakes while mirroring and skinning but knowledge i got helped me to build it up again in very short time. Thanks for your responses!

rred-izak Wow, great respect for starting with Piero's rig as your first rig ever 👍! Practicing is the best way to getting more familiar with rigging. It's important to understand the basic principles in order to become a good rigger and maybe find a better or simpler solution for a certain rigging challenge. You're headed in the right direction 😀👍!

It's because one of my friends suggested me this course xD but yeah thanks guys, I'm happy how it went out

rred-izak That's awesome 😀! You perfectly nailed Piero's different emotions 👍! It reminds me that I could finish my Piero even though I currently have so many projects in the pipeline that it's sometimes difficult to decide which one I should prefer 😉.

Please finish your bird! as far i saw it it's more similar to Kent's art, mine is very parrot like lol. It was unintentional, i had problems retopologing the beak. Anyway keep on great work and thanks for being helpful soul  to beginner like me

rred-izak With finishing Piero, you've really won the jackpot 💎👑🥇🏆!!! You can really be proud of yourself 👍! I remember when I started modeling Piero for the first time and was caught in the idea that my model should match the orthographic side and front view 🤪. I needed to learn that I should go my own way and would never meet Kent's @theluthier Piero 100%. The second try was successful. With the retopology I had to mentally fill some gaps where things weren't that clearly visible or not visible at all in the video. Then I had to develop my own technique for painting the feather's because I only had Gimp which I was already quite familiar with. And then came the rigging 😱😬🤪😵🥴!!! So much that could and did go wrong 😉! But I've learned a lot and now I'm more confident than ever that I can finally solve every CG problem even though that doesn't mean that it's always easy.  But coming back to my Piero: At least his rig now has some nice colors 😉😁 (see here). I hope that I can match his face poses well enough. That's really an art for itself! By the way: Did you use any addon for the "Bone Layer Management". There is one that I mentioned in one of my countless comments 😉, but I didn't use it since I'm still hoping that we will get a "Collection" system for the bones as well so that we are no longer limited to 32 bone layers and can better organize everything.

I totally understand you! I also started piero 2 times, but i had problems with retopology. Retopoflow helped me lots and it also happen to be cg cookie creation xD

OMG these are some good control bones. I didn't do my control shapes bacause i have no time and I'm going into starting my own models soon from scratch but yeah yours are <3 I may also use yours for future reference
No i haven't used any plugin for bone managment sadly :< maybe someone will manage to create widget collection addon