Billy I have been doing exactly the same thing testing wise. I create a formation and use the IGE to quickly put potential players that could fill the position in my team. I then save the game before the first friendly is played and then play roughly the same 20 - 25 games over and over making slight changes every new save. This year I've chosen Man Utd as my team.
Until this year I only used OME as last year I tried EME but it was far too slow and boring. I stopped playing FMM earlier this year due to becoming tired of the same rubbish OME had to offer. I tried using different formations this year on OME but grew tired after testing religiously for 5 or 6 days.
I've since tried EME and after some days of testing I will never go back to OME. I have found the following while using EME...
1 - Player fitness is generally much better. Nearly all of my players can play game after game without being subbed off (As you've already stated).
Because of this I won't need anywhere near as big a squad as I would have using OME.
I did notice after playing the same players over and over, that 2 or 3 of my players condition deteriated quicker and quicker during matches as the season went on. Their stamina stayed the same though. I just left them out for a few games which seemed to do the trick.
2 - EME is much quicker this year. I occasionally watch the game but generally I have commentary only at the fastest speed possible, and the game seems the same speed as OME. I use a Samsung Galaxy S7 Edge. Don't know if that makes the game quicker or not...
3 - Tactics actually work!! I had read on this site that EME is more difficult than OME. I cannot disagree more. I've tried some crazy formations and tactics that work quite well. I've also sailed halfway through the league on 4 occasions without losing a league game. On the 1 full season I played I won everything. In the league I won 35 and drew 3. Only loss i had was in a 2 legged European Cup game - which I still went through.
4 - No more 1 shot 1 goal for the opposition! I hated how often that used to happen on OME and the excuses people used to make for it happening. Like it evening the game out or it happens in real life etc. It doesn't! Not that frequently anyway.
5 - Injuries are slightly harsh this year using the default training. Don't know if match engine makes a difference or not. I was making changes to training to see a difference in injuries but they were basically the same. In the end I cranked up training to silly levels and injuries stayed the same so that's how I'll leave it.
I'm sure there's more but I keep being interrupted at the minute :-D
All in all EME has brought back my passion for this game.