It wont mess up anything.After you mark it read-only client doesnt remember previous graphic options, so you have to change graphics to your own everytime you launch client. Ill maybe upload video confirming it.
I read about an experiment someone did a while back who deleted his RS Cache information after every logout on multiple accounts and they were all banned.
This is a bit different, but how do I know I'm not gonna get banned for messing with the kind of information Jagex wants to collect from your computer?