First time I heard about gobrrr website was in bitcointalk forum and I think they have very good prices for everything, especially when we know how hard is to find Raspberry Pi with lower prices on other websites.

There is nothing wrong with Orange Pill case and you can change it anytime if you do it carefully.
I prefer printing my own case with custom colors with freely available .STL files.

Any device that have RNG option is not really generating true random result that can't be reproduced, that is why we have TRNG, but wallets like trezor are trying to fix this with mixing multiple sources to create better random value, that is still not good in my opinion.