I have about the same experience level as the OP and am a vacation diver with no regular buddy. I think when you are inexperienced and diving with an instabuddy, you have different needs and expectations of a DM than if you are experienced in independent diving with a regular buddy.
That is particularly so if you choose the dive op on the basis that they promise small groups, experienced dms etc (which is what I do).
Personally, I don't expect the DM to set up my gear (although as a new diver I did ask for a check that I set up correctly, which was provided). I don't expect the DM to check my air (although most seem to do so), to tell me how to do a buddy check (but also to not rush me into the water without one), to wash my gear or to serve me tea
I do expect the DM or the dive op to give a proper briefing of the dive site, including any particularly challenging aspects of the dive, so I can decide if the dive is within my comfort zone. In the OP 's situation I would expect the DM to tell me that the dive involved entering an extended overhead system at 40m depth, so I could call the dive. They know the sites, I don't.
If the rules are that we are diving as a group, with everyone following the DM, I expect them to check that everyone is ok with entering a challenging environment, such as confined swimthrough, especially if it is not part of the briefing. And to not swim at breakneck speed.
I confess that I do see the DM as an extra safety blanket in the circumstances where I don't have a guarantee that my dive buddy is competent (or sane!). I don't necessarily expect that the DM could rescue me if a problem occurs, but I do expect them to not lead me into a dangerous situation that I haven't been briefed on.