If they are simply log files - records of installs, mis-installs, errors and so on - then you should be able to delete all of them if you wish.
However, I'm a bit concerned re your question about files loading at start-up - are .log files loading at start-up? If they are (1) why? and (2) leave well alone.
If these files are not loading at start-up, and you have plenty of disk space, again I would leave them alone.