I'm a current LLB/Politics student at Glasgow. It's a great course and a great uni!
I got my offer around early December for both Glasgow and Edinburgh. I think I got Strathclyde a couple weeks after I applied.
I would strongly recommend that you do 6th year or take a year out and take deferred entry.
Firstly, university is a big jump academically. I did 3 advanced highers and honestly I'm so glad I did because it was the best preparation for uni. I had an unconditional so I didn't have to do them but I learned so much and it was the best preparation for uni. For me highers were about memorising formulas, analysis handed out by the teacher, and learning was all geared around the exam and coursework. Advanced highers allow you to develop your academic skills: they're a lot more about thinking independently, having the space and freedom to explore learning by yourself. This course is a lot of reading, writing academic essays, being really self-motivated, having to think for yourself, learning completely new skills and I felt that I was able to start developing these skills at advanced higher.
Secondly, it isn't ideal being underage in 1st year. I was 17 for most of first semester and it's a lot harder to fully embrace university life if you can't go on society socials, are stressed out about getting in, buying booze etc. However, it is possible: I survived, my friends survived, and also you don't have to be involved in drinking culture to have a good time at uni. It's also about being mature enough for uni and having the life experience that it takes to live independently. My sister's your age and honestly, I don't think she could look after herself. However, I'm sure you are probably very mature if you're applying to uni this year.
Thirdly, you're still young what's the point in rushing? I kind of wish I'd taken a year out just to have a break from academia because I felt exhausted after finishing school. If you're predicted AAAAA then you're pretty much guaranteed unconditional and so why not do 6th year to spend time with your friends and take the pressure off for a year.
However, if you are going to go this year...
Firstly, get ID if you don't have one and you want to be going out. (but going out is not essential to have a good time at uni!!)
Secondly, learn to cook a couple meals; take over making calls and appointments if you haven't already. Some people come to uni and are seriously a mess in terms of looking after themselves.
Thirdly, try to step up your game now - think about how you take notes, how much external reading you do, how you can study smarter, how you can mature your essay writing (making it clearer, more relevant, bringing in your own analysis). It'll make the jump way easier because at uni you're mostly on your own in how you approach your learning. Lecturers give you the facts and expect you to come up with the analysis. There's much less support on how to write good essays and revise for exams.
I'm really enjoying this course, I think law and politics is a really good combo because they compliment each other but also give you a bit of variety - I think I would get bored if I was doing straight law. if you do decide to come this year I'm sure you'll be completely capable.