I had an FNX 45, and still have an FNX-9. The -45 Tac excels at being optics/suppressor ready out of the box. It's a big gun, but not huge. Think of it like a second draft of a Mark 23. What that pistol was, but refined a little and run past an editor to knock off some of the over the top parts. I sold my because someone offered me enough money that I couldn't refuse during the Obama years. If you are thinking of running a suppressor and optic on your nightstand gun it's a solid option, but there are more choices now. I think an M17 would probably beat it in shootability.
The FNX shoots...OK. It's trigger is ....OK. Ergos are.....OK. The gun is a solid performer. I paid in the $400's for my -9 and it's a steal at that price. I have kind of a fetish for mid-sized 9mm pistols, and it fit's right in with that group. I will say I find the checkering to be super aggressive for more than 100 or so rounds unless I have gloves on. I've shot some matches with mine and it can be run fast pretty easy.
It's kinda weird. FN makes a solid gun. The FNX does everything it tries to well, but excells at nothing. It's...OK. I rarely reach for mine when I want to go have fun at the range, but I leave it loaded on the nightstand with a TLR-1 on it, and trust it completely. When I do take it to the range it functions flawlessly and hits what I point it at. I just don't really love it. It fit's kinda where it is in this wheel. Right in the middle.
I had the same idea about the manual of arms thing when I got mine, and almost never actually use it that way. In actual practice, and I think more so if groggy, I muscle memory swipe at where the safety should be on any pistol I pick up, and then pull the DA trigger. Actually trying to train with the FNXs cocked and locked is one of the things that started my transition to Sigs, actually.
Also: Obligatory shot of the Belgians, because they don't get enough love: