I just had a purple line appear on my pixel 8, google offered me $490 on trade for a 9. The line is intermittent so I just rated my phone as good condition for the trade in. There is an extended warranty on the problem so if they try and give me any shit about it I’ll just reference that. If you do trade it in, make sure to uncheck the box that says you’ll accept less on the trade if they decide the condition isn’t as described. I have no actual evidence, but given my fairly extensive history dealing with googles customer service I think they may try and screw you over on the trade.
The IMEI number on the phone is essentially locked to the device, swapping sims won’t change it. So a phone activated under your real name on one network could technically get traced back to you even when using a different SIM card.
Also, carrying a phone with both SIMs active is completely unprotected from correlation attacks by anyone with access to the cell tower data. It’d be blatantly obvious that the location of one SIM is the same as the other all the time.
All depends on the threat level you expect, but if you’re worried about a VOIP account being compromised to get your real number, you are talking about pretty sophisticated actors.