While there is a difference in beam from an S2 to an S2+, it really isn’t huge. And you’d need them side by side to really tell the difference.
Also remember the Nichia is smaller, so will produce a tighter hotspot and be a little more throwy anyhow.
Basically, what I’m saying is, I don’t think it really matters which reflector or host you’ll use.
You can also drive a Nichia much harder than 1.5amp too, but of course you don’t have too. But do remember it won’t be as bright as the Cree’s.
As for the other things you mention, AR lenses are proven to work. But the reality is, I doubt you’ll be able to tell by eye. And I’d argue and say for a 1.5amp driver a braided tailcap and over large wires won’t really net you any visual gains and just make the build more hassle.
I have a couple of Convoy S4 hosts that I’ve modded. One is a Nichia219B on a Noctigon and running a 3.04amp Qlite driver. With a good battery you will see 2.99-3.04+ amps at the tailcap. This works well as a short burst use light, but does heat up quite quickly, i.e. you couldn’t leave it on high and go for a 30min+ walk without over gloves. But for a few mins use at a time, it’ll be brilliant and quite bright still.
I didn’t use any spacers or centering rings. On this build. Just the stock components.
Medium mode pulls 0.78’ish amps, which is quite a useful level, as it’s still fairly bright and you can run it on this level until the battery goes flat if you want too, with no heat issues.
That said, if you want the highest output, for the longest runtime, then a different driver would be needed, as the Qlite is way above, or way below 1.5amps. Honestly, if I was doing this again, I’d not buy a host. I’d just buy a complete Convoy with one of their drivers in, the 2.8 (8*7135) is almost as good as the Qlite. And simply swap in a Nocitgon with a Nichia on. Sure you can do all the other bells and whistles. But I struggle to believe they’d make any difference if you plan to EDC it.
Convoy do a 1.4amp version of their driver, which might be bang on for what you are after.
For the record, I also built an XP-G2 Convoy S4, using a Qlite and a Noctigon. I went for the R5 5A2. This is a lovely NW high CRI led. Ok it doesn’t claim as high a CRI as the Nichia. But I tell you what, it’s a really nice tint. It’s slightly brighter than the Nichia (visually). And I can only tell the tints apart when I have them side by side, and even then it’s hard to tell. If anything the Nichia looks a little blue/green next to the 5A2.
Nichia S4:

And here is the Nichia and the XP-G2 R5 5A2. Not the best comparison pic, but clearly shows they are very similar:

And to prove the point, here is the same Nichia against a cool U2 bin XM-L:
