Brand new to this

[BoxcarPete]

Low tidal volumes aren't necessarily anything to be worried about on their own. What's your height and weight again?

[Cheesedream]

I'm 6ft, 225lbs. Fairly muscular but a bit of body fat aswell if that makes a difference

[Cheesedream]

From a quick Google search I've found that tidal volume should be 6-8ml/kg.
So for me thats over 600-800 and most nights it's been less than 450 at this current setting. I don't think it went higher than 550ish on lower pressures either.
My insp/exp breathing is pretty even again now too where i had higher exp than insp with lower pressures. Does that mean the tidal volume is more effected by my expiratory rate?
On another not that I don't think I've mentioned, my nose breathing isn't always great. It always feels partially blocked and when doing a covid test I can only get the swab in my right nostril and not my left.

This all might be irrelevant but I'd like to rule everything out.

[BoxcarPete]

Tidal volume is a fairly broad range, and more closely correlated to height than weight. The reason for this is because your lungs are situated within your thoracic cavity, bounded entirely by your bone structure. No amount of muscle or fat you add or take away changes this. I'm a couple/few inches taller than you and low-mid 400s was where I trended before my nasal surgery, now I track high 400s up to 500.

Minute Vent is more correlated to weight and metabolism, because it represents how much air per minute is exchanged within your lungs. I am 205 lbs and often would only see 6-7 L/min, now I'm seeing 7+ for the most part. Modest gains, but on my good nights I'm seeing fewer spontaneous arousals that I had always suspected were related to underventilation.

As to why your pressure setting may be affecting these stats, that has me scratching my head. If you know you have nasal obstructions it's worth getting scoped. It might not fix everything, but improving nasal breathing is likely to make PAP more tolerable.