Top case choice

Hello everyone. I've ridden my 310 GS with a soft bag on the rear but I'm ready to upgrade with a monolock case.
I looked at shad and givi .looking for something not too round, not too boxy...
I also do t want to feel like the box is out of proportions compared to the bike. So wondering what size I should look at to avoid that but also be able to fit one full face helmet and a jacket.
And last, givi has this top box that you can connect for extra break lights which I like a lot to add to safety .

Any thoughts? Pics of what you've done with your 310's GS . thank you in advance.