I recommend 2k clear as well. Andy is probably right that it's only a bit tougher, but it's like puncture-resistant tyres: enough is as good as a feast. Spray.bike with its own clear coat gets chipped off during normal winter riding on a bike without fenders. This is not acceptable. I completely stripped and repainted that frame recently with the same colour and 2k clear. It's now glossy and lovely and easy to clean (but I haven't tried it in the winter yet).
Anyway these are my tips:
1. Let the 1k colour coat dry properly, like several days indoors or somewhere hot, before putting the clear on
2. Make sure you buy the glossy one if that's what you want (it has 88E on the can). They also do a satin and a matt.
3. Only spray it outside and use a respirator as well. Safety glasses also a good idea because it gets in your eyes depending on the wind.
4. Don't get any on your or your neighbour's car.
5. If/when bugs get into it just leave them there. This is better than trying to get them out when it isn't dry yet.
6. You can build up the bike carefully after 48h but I wouldn't clamp it in a workstand yet-- it can take a month to reach full hardness.
My favourite for the paint underneath is Montana Gold primer and colour. But spray.bike is OK too if you keep the can nice and close to the work (or you get annoying powder everywhere).