SO's are only that until they've finished their line training sectors (it's a lot of sectors, either 120 or 140 off the top of my head). Takes about 6 months on the A320 and over a year if you get on the widebody.
SO's are not cruise pilots. They are occupying the RHS from day 1. SO only refers to the restriction of sectors / having to fly with a line trainer.
Can't comment on the SO wage (think it's about 10 or 12K QR plus sector pay?). As a widebody FO I was clearing about 26 to 27 thousand Qatari Riyal in the hand every month, plus free accommodation provided. No tax of course. I think if you compare it on a cash-in-hand after-tax basis, you'll find that's more than most RYR captains make, let alone FO's. Especially considering you're not paying rent and considering all the stealth taxes in UK / Europe like council tax, VAT, TV licence, fuel tax (used to spend 3 or 4 hundred quid a month just filling up my car in Britain, it's virtually free in Qatar of course).
The down side is that the airline culture is brutal and fear driven, one mistake and you're out, trash talk the company to the wrong person and then find you've been reported and you're out, forget to wear your hat on the walk round and you're out, get caught with a cabin crew girlfriend and you're out. Etc etc etc.
The training is generally of a very low standard and it's also fear driven with very little positive feedback or encouragement, parrot fashion regurgitation of the ops manual is encouraged, using your brain to think laterally and solve problems is not. Get used to saying "yes captain I see captain" a lot, even when the guy is an ignorant third world buffoon, they can make your life hell if you disagree with them. RYR would be streets ahead in terms of training standards and actually becoming a "good" jet pilot after a couple years on the job.
Other big downside is the town itself, it's a completely desolate sh!t hole with nothing to do except hang out in the malls, or drink in a soulless and stupendously overpriced 5 star hotel bar where guys outnumber girls 10 to 1. It's not so bad if you're single and a gym rat or prone to other solitary pastimes, but think very very hard if you have a family.
As an expat cadet you'll 99% likely go on the A320 and that's another whole can of worms with regard to rostering and fatigue, consecutive night turnrounds to the subcontinent and min rest in Doha, go read the threads in ME forum because the guys there tell it like it is better than I can, it's a big and very serious issue in terms of safety as well as lifestyle.
As a wannabe you'd have to take the QR job over RYR if you got it, just because you don't have to splash the big cash for the rating. TBH they're both stepping stone jobs though, bend over and squeal for 2 or 3 years and then try to get in somewhere decent with a sustainable lifestyle
