i use the X52 pro (YAY metal parts so i don't accidentally bash it!) and my friend uses a 55.
1- the bases combined (on 52, think 55 is slightly bigger but roughly same size so no prob) are about the size of your keyboard, i had a similar problem but got a plank of wood and duct taped it to my desk so i know have each hotas platform on either side of my keyboard as apposed to behind my keyboard and having to reach over it as previously.
2- 3- your right, the 55 cables are separated and the 52 plugs the joystick into the throttle, which goes into the computer. i assume the 55 is same or longer from what my freind says. although on my 53 the joystick to throttle cable is a good 2ish feet of thick wire, and another 3-5ish feet from throttle to computer. and the cables plug in halfway up the base back which si an inch or 2 off the desk so i don't have problems shifting them around to grab my xbox controller when i hop on GTA or just during regular gameplay on elite. the cables are really not a problem in this.
4- ive done lots of research on these because i was a bit picky for pricing, and dint want something my clumsy ass was gonna break. definitely recommending the 52 pro (over the 52 normal) as the pro version is made with higher grade and metal parts removing almost ALL wear and tear and rough housing problems of breaking it. the 55 is the same bust costs much more (buying used, was bale to get my 52 under £50 and i couldn't find 55's under £100 so). if costs isn't an issue then its preference. the 52 has all the 'extra' buttons spread between the joystick and throttle, which i like. the 55 had all the 'extras' on the throttle meaning one hand is responsible for any ship 'systems' in elite, which my friend likes. the 55 looks a bit more professional, but the 62 has an LED display thats SUPPOSED to have loads fo functionality with LOADS of games (such as it shows airspeed and things in games like war thunder for better immersion) but i cant be botherd/ haven't been able to figure it out. they both have dual triggers, and the only other differences between the 52 and 55 is the 52pro has a 'safety' flap over the secondary fire button (which i LOVE to keep myself from accidentally firing weapons in games id rather save and not fire on accident) that the 55 doesnt have, BUT the 55 has duel throttles (it splits) which the 52 doesnt have, but i can't find a purpose yet for said dual throttle other then making WT tanks way more realistic, but i guess its just as useful/useless as the 52's LED display. unless you literally throw , both HOTAS stick to surfaces VERY well, and wouldn't recommend any other then these 2 hotas unless your budget is way less then £40 ($60) or your budget is WAAAAY higher and you want something SUPER-SIM like the a-10 replica joysticks and such.
as for getting a HOTAS in general i highly recommend it. it makes everything WAY more satisfying and immersive. on elite you can completely tell a hotas user form a mouse player. dunno about star citizen's i'm a bit too poor to pay over £100 just for a ship (although i've heard its another game that compliments hotas users). and in WT, well, unless you're only gonna be in simulators (where hotas excels) then your gonna get outmatched by every mouse user due to 3rd person game mechanics).
