In reply to Duncan Campbell: Left Wall Traverse is more like 7c+ but I don't think the benefits of doing this (a traverse) transfer so well to vertical routes but you are getting pumped / recovering etc so I guess they must to some degree!
I'd like to suggest 7s that have more of a trad style but there really aren't that many around I think. In fact Rub a Dub Dub on The Diamond is about the only one that comes to mind (felt very like Right Wall to me). I belayed someone on Non-Tidal Screamer, also at The Diamond, not so long ago and that looked a similar style though obviously somewhat harder.
Most sport routes in the grades you're after in N Wales have bouldery cruxes or are short power endurance affairs. Libertango is a good idea as is La Boheme, both being vertical and crimpy climbing. Nearby you've also got Pink Pinkie (my first UK 7a onsight so definitely at the easier end of things). There's quite a clutch of very worthwhile (crimpy, technical, decent finger strength needed) stuff in that area: Face Race, Mean Mother and Night Glue (also steep and physical near start).
To be honest I think the biggest benefit from sport (for your trad) is having a very good idea of how far you can actually keep going. Most people never climb trad (or sport for that matter) until they fall so they never learn where that point is (I'm talking physical routes here not something technical where you fall due to footwork for example). You can do precisely this with sport. Sport also shows what you can recover on, again really useful for trad where, on most things (can't comment on E6 and above) there's a really good rest or jugs just before or after a crux. If you know you're going to get a rest after a few metres of harder climbing then you can go for it. Equally, you develop the ability to 'rest your way' up things.
In no order some other really good 7s in the area are:
Technicolour Yawn 7a+, Dinbren
Walking with Barrence 7b, Dinbren
The Bandits 7b+ (hard), Dinbren - one of the best anywhere at this grade?
Grand Canyon 7b+, Devil's Gorge
Pearl from the Shell 6c+ (tricky), Llandulas
Searching 6c+ (7a?), Llandulas
Prime the Pump 7b, Llandulas - very continental (if it weren't so short!)
Boat People 7c, The Diamond - sensational but hard, also quite conditions dependent
Ocean of Emotion 7b+, Wall of Detritus - gobsmacking and really quite trad, you follow a sort of crack feature in the upper half, it's pretty 'out there' generally, the bolting at the top provides for plenty of air time and the climbing itself is face then crack
The Mask 7b+, Pen Trwyn - overlooked but a great power endurance route, steep so different from quite a few of the routes upstairs
Mayfair Wall - do the lot and you'll be well-equipped for trad wall climbs! Everything I've done there has been good.
Further right:
Bearded Clam 7a+, Pen Trwyn - awesome
Plagued by Fools 7b+, Pen Trwyn - tough, bouldery crux but very satisfying
Actually I'm going to stop there as you'll get something from all the sport routes upstairs at Pen Twryn so get on them all!
With regard to trad to go at, a few others to try:
The 3 E3s beside each other at Pen Trwyn (Klondike, Pocket City and Solid Gold, P City felt tough at E3)
The Visionary, Pen Trwyn - felt very soft for E4, take small / medium cams
What a Difference a Day Makes E4, Hidden Wall - you can lace this up at the top, steep and safe
Memory Lane E3, Cromlech - no way as serious as made out, good but spaced (though not excessively so) gear all the way except maybe upper arete but the climbing is OK here, amazing position and lovely face climbing
Strike E3/4, Upper Tier - perfect for what you're after
Poisoned Arrow E4, St Govan's - more like E3, really nice, open climbing
Tangerine Dream E4, St Govan's - outstanding and quite hard but safe
Enjoy!