We used the kits & such out of the Complete series, NWP, & Secondary Skills.
A lot of other stuff got tried once or twice & discarded (like psionics).
The hardback Options series were simply disallowed. We, the group I played with when this was new, read this crap, discussed it, fiddled around with it in a few test sessions, & decided Hell no. We didn't want our occasional D&D game (we were shifting away to other systems & only played D&D about once/month) morphing into that kind of complexity & min/maxing.
Still don't.
2 years ago our long running (2012-2016) 1e game at the local shop more or less ended. We should have called it done & moved on to a new campaign. But enough of the other players really wanted to finish the adventure (Night Below) as we'd already invested 3.5 years of real time to playing it. The DM agreed & decided that everyone should make 2e characters - with the same # of xp (not lvs) as our previous characters . Despite only himself, me, & 1 other person (we'll call him Joe) owning any 2e books. So everyone else ordered the 2e PHB reprint & the shop gave them a discount.
At this point Joe brings up using the Options books. The idiot DM likes this idea. (WHY I have no idea, he was already complaining about the complexity involved in DMing for 11th lv 1e characters....)
Of course the other players ask "What's that?"
Joe & the DM explain. Filtered through the rosy lenses of nostalgia.
I offer my opinion on the subject & warned the group about the coming complexity, min/maxing, & shear brokenness of some of it. And I reminded the DM of how he's having trouble with 11th lv 1e characters who's options top out at UA.
My recommendation was ideally we don't use any of it. But if we do, only use SOME of it. Look through it & make a few decisions as a group. Maybe start from scratch at 1st lv so you're not trying to immediately digest a campaigns worth of options all at once.
I should mention that this group consisted of 8 players + DM.
We put using it to a vote. Several people abstained (didn't care/were just undecided). Of those left, those that thought Options sounded good won. And they voted for using everything. OK, I warned you, & voted against doing this, you're going to find out why 1st hand....
Oh, and I'm NOT making my copies of this stuff available. I'm not going to be complicit in the coming train wreck, so you should go on-line & buy your own stuff or pirate some PDFs.
Nobody did that (at this stage).
A weak later the new 2e PHB have arrived & it's character creation night.
Joe & the DM bring ALL the options. Options books, the complete Complete series, the multiple volumes of the Spell & magic item encyclopedias.... It looks like 2 gamers libraries just landed on the table....
The other players were overwhelmed.
And of course there were only two copies of anything. To be shared between 6 people. Who had to read through it all because they'd decided that all options were a go. (Joe & myself already had our new characters made)
Joe & the DM attempted to help.
Myself & the shop owner stayed out of the way that evening.
Character creation ended up taking 4 weeks & costing several people even more $ as they decided it'd be easier to use this stuff with a book of their own.
The resulting game? Lasted 3 weeks.
You should've seen the frustration radiating off of the DM as he discovered what properly min/maxed, custom built races who were Duel/multi-classed, with custom class features, variant skill, stats, casting options, etc could do.
Oh, and almost everyone of us were some mix of caster.
And turns took forever as people weren't familiar with all the crap their already high lv characters could do.
We never did finish Night Below.