These are, more-or-less, "department store scopes." Made in China, but likely lower quality than those made by Synta, another Chinese company that owns Skywatcher and Celestron.
The optics might be decent, but the build quality, particularly in the mounts, is likely poor. Everything will feel loose and rattly... Generally speaking, you want a mount which is as sturdy as possible. Every vibration is magnified as seen through the eyepiece, after all.
The price is also hardly what could be considered a discount. It's about what one would expect to pay for these particular scopes.
If I had to pick one, I'd go with the RP-200 80mm refractor. It has the simplest mount and and the shortest tube, and will therefore be sturdier than the rest. I would then add a decent-quality 90-degree mirror star diagonal, and probably a red dot finder as the included finderscope is useless. After that, it wouldn't be half bad as a travel scope.
The RP-100 has a wobbley yoke mount which will cause nothing but frustration. The 300 will be unstable on its mount as well. The 400 is probably okay, but I'd rather save my money.