As far as your first question.....
I think there is a lot of hangovers about OP Eldar from the previous editions, mainly concerning how many D-weapons were being thrown around on relatively mid-points priced units. Alongside that Wraithknights were absolutely horrendously and seriously underpriced, and you could pull some cheeky shenanigans with Warp Spiders and Flicker Jumping.
Fast forward to the current edition and obviously D weapons don't exist plus the Wraithknight is now super expensive for what it delivers and its effectiveness compared to an equivalent Imperial Knight.
I play Saim-Hann but I only use a single unit of Wind Riders. For me, that Craftworld is all about the colour scheme. The combination of red, white and black across the core standard units in the codex is great; vibrant and contrasting.
I use two Farseers, one one a jetbike and the other on foot, with a combination of Wraithguard and Wraithlords and air support from two Crimson Hunters and a single Hemlock. So, although I gain the benefits of having resilient Wraith type units, I lose out on the Iyanden benefits and don't hugely gain with Saim-Hann due to only one unit of six jet bikes. Therefore, although I've never experienced anyone moaning about taking Eldar units out of a case, if they were to its fairly clear the once you actually look at it, I'm not exactly stacking the deck in my favour for rules.
The aspect of my army that people don't like is the aeroplanes rather than the 17 Wraith models because the aeroplanes move fast, turn quick and can slag vehicles fairly quickly.
I even chanced my arm and took a Revenant Titan to a 100 Power Level tournament weekend at WHW earlier this year. And guess what, I didn't win all five games because first turn is just as pivotal in modern 40k than the actual armies on the table. Regardless of how hard and army is perceived to be, first turn and shooting the backside off of it will really skew the playing field. An army is only as good as the general marshalling the units and making the decisions.
Based on the units that I use, Wraithguard are really resilient. Clearly, getting shot at by -3Ap guns can really hurt but when five Wraithblades can walk away from 30 Ork Boyz at the expense of five wounds lost, I'll take that.
I don't use Wraithknights because I personally don't think they are worth the points cost. A 500pt+ bullet magnet dying by turn two is rough to say the least. Even just losing wounds and then dropping in effectiveness is enough to put the final nail in the coffin of that unit.
I love the aeroplanes simply because I like aeroplanes. Some people elect to use three Hemlocks, each to their own, but that is really disgusting in my view.
I'm adding in some Harlequins currently for some close combat option. Why not Howling Banshees????? Easy, Harlequins are plastic. Howling Banshees have been one of my favourite looking units in WH40k since I started the hobby in the mid 90's but I don't like metal models and I like finecast even less, ergo, Murder Clowns instead. Plus I can paint them in a style that compliments the Saim-Hann colour scheme.