Is it easy to delid by myself at home?
It's easy if you have der8auer delidd tool or rockit99,it's almost fool proof.
But stay away from razors and home made tools because there is 99% chance that you will damage some of the caps or other components on CPU PCB.
Also,forget about AIO on i9s....Only custom loop will give you descent results and after delidding,you need to do some fine tunning to keep OCtemps to acceptable levels.
They are great as workstation PC.It's not cheap,it's not that easy,but results pays off (note,I have a dud for i9 7900x on full blown custom loop,barely OCable but great for my work nevertheless)
I think if you go for threadripper,you won't see any significant performance drop,but you will save like 1000$ on mobo and cooling ...