Fucking dumb ass question but how do you know if your bitcoins are being held in a SegWit or Non SegWit address?
If the address begins with 1, they are definitely not Segwit coins.
If the address begins with 3, they are held in a P2sH address. They could be segwit or could just be a multisign address. If the private keys are under your control, you should know. Likely they are a segwit address since you would definitely know if you set up a multisig address since it involves a very complicated process to set up. If the private keys are under someone else's control, like an exchange or online wallet, you will need to research or ask.
If the address begins with bc1, it is definitely a segwit address.
So its a lot safer if my bitcoins are all held in addresses beginning with a 1
Only if you believe that a fork that will treat and spend segwit coins as anyonecanspend transactions will eventually become the chain with the most work. (And also the chain with the most economical support.) Your segwit coins will be basically unspendable on this chain. As soon as you attempt to spend them, you can only use the segwit redeem script which the miners will appropriate for themselves as an anyonecanspend.
Your segwit coins are safe and sound on any fork that enforces segwit rules.