Always nirensei as both colours. Always approach 3-4 low, and about 50/50 between approaching a 4-4 and invading it.
I tend to think my repertoire is more about joseki sequences and post-joseki aji and potential.
When I’m black I usually play O13-H15-D11 (Sofia Fuseki at Sensei's Library, thanks @bugcat). I change it a bit if white plays on the top. When I dont want to play it (usually because someone asks it) I play the Chinese fuseki or sanrensei.
I didn’t find a valid alternative with white. What I usually do is 2 komokus asking to cross corners, mirrors go or approach every stone played by black.
Lately i’ve been playing (as black) dual 3-4’s + enclose on move 5, especially if white plays 4-4’s (mmmm tasty 3-3 invasions…)
As white its bit more reactive, but i generally play the first stone at 3-4 facing the diagonal corner of blacks first stone, and after that im mostly just reacting on what happens on the board. It feels that pretty much all fusekis are meant for black to play, as its really hard to implement any kind of strategy when being a move behind the opponent.
For me it was the opposite. Limiting my joseki and fuseki to what the modern pros are playing and then studying pro games has definitely boosted my winrate, though it was part of the overall improvement package. But generally I can confidently go toe to toe with much higher ranked players if we both play the modern opening, for example my game vs ternamja recently, which would’ve been him +5 to +7 if I knew the ko sequence in the corner.