Option 2 is much better. Do you speed work then throw in 1-2 gassers or a 300 shuttle. Its almost like when you are training for track we do our neurological technical speed work first then sometimes finish off with a special endurance rep. which is fine.
Should I adjust any of the volume for my two speed days when I do this? Your reasoning for the gassers and shuttles makes sense to do (and I would likely spend most of my time with those), but is there any major reason why you couldn’t do some sprints with some limited recovery?
Also, for speed work should football players go out of a sprinters stance, their postion stance, or just stand up and run.
The first thing you are describing is split rep speed endurance and could work, but is much more taxing than the gassers I think because they are performed at higher speeds. As for what to run out of, I don’t think it makes that big of a difference. A standing start would reduce the demand that a lying start or 3 point start has, which may be better for high volume sessions.