Hi everyone,
I have two questions. What is the impact of a head coach and the other coaches.
Also I don't have a lot of experience with drafting. Could you give me a few tips about how to draft?

Head coach determines what plays you have in your playbook, other coaches aren't really all that important (though it's better to have them from a training camp perspective).

And insofar as drafting, I endorse ArmoredGiraffe's approach to it quite highly:
https://docs.google.com/document/d/1Tu0Sy1SbseNx_zuB-DosfgeKTJ_J35qk/edit

Head coaches currently do 1 thing and that's give you your offensive and defensive playbooks which determine which plays you can call.

As far as drafting goes, you want to draft non-lineman who have more than 80 speed. Volatility does not determine how likely a player is to improve or get worse during training camp but determines how much they will do either of those things. The guide posted was written by me but it is a lot to read. My general draft strategy is to draft the best, fast player available regardless of their volatility in the first couple of rounds. Nothing is more important than your skill players

Edit: and in later rounds almost always draft the highest vol players you can as there is a late round bonus that gets applied to their rating and a 7th round pick can improve a whole lot

Thank you guys for all the advice and help.

QBs need high accuracy the most IMO.

RB/WR you want at least 80 speed but pay attention to their actual physical weight as rookies have varying weights but once in the league, their weight will gravitate to the norm for their position. Players gain/lose 1 point of speed for every 7 pounds they gain/lose, so a player that needs to gain weight will get slower.

For example, you draft an 80 speed WR that weighs 184 pounds, but most every WR in this game weighs 198. When he gets to 198 lbs, his speed should be 78. Take that same 184 lb rookie and make him a 217 lb RB? He'll drop to 75/76 speed.

Same in reverse. Say you draft a 259 lb TE and move him to RB. Eventually he'll drop 425 lbs and gain 6 speed.

If you want to know the default physical weight for each position, take a look at any roster in any league. The ones off the top of my head are 198 lbs for WR, 217 lbs for RB and 276 lbs for DE. Weights also vary between CB, SS, and FS, the OL positions and the LB positions.