1, I find that Tom is not a nice man. correct, and it means that you are of the opinion that Tom is not a nice man.
2, I find out that Tom is not a nice man. also correct, but this one means that you have learned that he is not a nice man, you've gotten that information from somewhere/someone.
Do they sound fine and mean the same?
1, After further investigation, I find I've found that all these this evidence( without the s, because evidence is an uncountable noun ) were was ( because it now corresponds to the noun evidence ) invented by others.
2, After further investigation, I find I've found out that all these this evidence was invented by others.
Both are correct, but their meaning is slightly different.
This is a great question though, keep up the good work!