Workplace pension - tax and PFIC questions

I'm getting a bit confused reading other threads, so I'll post my own:

I'm a dual citizen, just moved to the UK last year for the first time. I recently started a job with a pension scheme, specifically through Aviva - it's a 'workplace retirement account,' part of the Aviva Master Trust. I'm hoping someone can enlighten me on the following items:

1. Am I correct that this 'master trust' pension is not a SIPP or private pension scheme and cleanly falls within the pension treaty meaning there are no tax ramifications until distributions are made? If so I'd like to max out the employer contribution. Then just forget about it (although I guess once the balance is over the FBAR limit, it will need to be listed there).
2. Are there any PFIC issues to worry about, or is that not an issue for a pension? I see Aviva will let me make some choices about funds, but I'm sure anything I chose would run afoul of PFIC rules.

I assume my existing US 401Ks and IRAs are also exempt from HMRC until I take anything out? I'm planning to just set any dividends to automatically re-invest. (Although I suppose I could use money from my US bank account to contribute to, say, a Roth IRA if that makes sense for my US taxes.)

Thanks, all. This is SO confusing for those of us who aren't financial or legal experts.

I can say for sure that HMRC are only interested in 401ks, IRAs etc once distributions are taken.  Roth distributions are also HMRC tax free.

I’m also now confused about the IRS treatment of UK 401k style pension schemes. (I’ve never had one, just the old fashioned final salary schemes in the UK)

You don't need to worry about PFIC reporting in pensions.

This pension is the same as as a work place nest scheme for tax purposes are these considered trusts? I found an old topic from 7 years ago discussing this when they were introduced though did not find any further topic of how they are treated.

Do these get treated like normal UK pension and only to be noted when taking distributions at retirement?