I get Pretty high off it every time i take it. Not blasted high but high enough. I tried 60mg first time and was quite impressed and it lasted like 12 hours. Yeah, there's no initial intense rush, but I feel it after an hour and it feels great and lasts so long that it makes up for that in my opinion.
The lowest I tried was 20mg, and that felt good too, not really high, but decent high. 40mg feels perfect i think, without adding more sides and shit. 60 is more intense obviously but then i start to have some mild anxiety and feel a bit sketchy for lack of a better term. The thing is, I dont have a script, and can only get it once a week or less depending on how well its hidden from me lol But if I had a bottle of it on me to use at will, would I take 40 or 60... probably 60, but being i get it the way i do, 40 is just fine. I think this is a best case scenario for me actually as i wont build a tolerance and wont get addicted this way. If i had my own script, I'd F it up for sure left to my own devices.
There is no way to potentiate it in the sense of physically breaking it down for insufflating or injecting or any other route as OP stated, which is the way it was designed. If asking how to get high from it, you must mean more of an intense rush i assume?? ..as it gets you plenty high as it is. Maybe you have a huge tolerance, in which case you will need much more to get high, but you wont ever get an initial big rush type of high that you get from an instant release amphetamine or snorting or injecting. This doesn't mean you don't get high from it though.
Ah yes, i tried a couple 20mg chewables as well and they acted exactly the same way as the capsules. Tasted minty... nice
From Drugs.com:
Ask your doctor before using
magnesium oxide together with lisdexamfetamine. Using these medications together can increase the absorption of lisdexamfetamine and may increase its effects.
I assume this means something like it will make 40mg feel like 50mg maybe lol But its still not gonna give you some big blast or rush you may be hoping for. I could be wrong though, I'm no doctor or pharmacologist

Remember to ASK your doctor if you plan on mixing the two though haha
I actually love this stuff, but i haven't tried adderall to know how it compares to vyvanse or if i'm missing out on something better.