I am really no expert about the keyboards and if the output is the same. It looks logical as you say it, but then why those virtual keyboards exist? At least I am not making my chances to be hacked higher I hope.
The software wallets as electrum are open source. The trezor I assume are not. I am usually not fan of geek's solutions and the ones from corporations work better.But with Bitcoin it seems to me as en exception and the community does good job with debugging.
I will be happy if you correct me in anything. It is not possble for me to test everything. Now I will make a new cold wallet for the affiliate payments and the old cold wallet will be completely frozen and not touched for ages. But even the new wallet will be portable electrum. So I will probably have no new experience with the wallets. But it is possible and maybe even probable there are some better ones.
If you talk to God, you are praying; If God talks to you, you have schizophrenia.