What are the benefits and downsides of relying on a TPM

The downside is that your PC gets locked down and perhaps excluded from services. It also serves as a unique hardware ID, even if there are alternatives for those. Some games and streaming platforms already use it to "validate" your device.

There are some very theoretical security benefits. You can also achieve those without TPM, but it might be a little less convenient subjectively.

But it mainly serves to lock you up as a user. You own your OS a little bit less. Overall it is not a good or sensible solution to modern security concerns and I would recommend to deactivate it.

Some security researchers might disagree and there is some benefit in corporate environments. But those that deny its problems completely aren't worth the money since their security scenarios will be lacking.