Some of our defaults settings are not optimal, and I think we can stick more to iMOD5.
We can argue that not all of iMOD5's defaults are optimal (thinking of #1391).
But I see other default settings as well in iMOD5 which are nicer:

Allocation

For DRN, we now have: ALLOCATION_OPTION.first_active_to_elevation. iMOD5 has ALLOCATION_OPTION.at_elevation, which fits tile drainage better.

For RIV, we now have: ALLOCATION_OPTION.stage_to_riv_bot_drn_above which is the most advanced option. Adding drains as well, which might be counter-intuitive. iMOD5 has ALLOCATION_OPTION.stage_to_riv_bot. I think this is nice enough.

Distribution

When we change the DRN allocation, we can also choose a much simpler conductance distributing option. We can stick to what is chosen for the GHB here and use DISTRIBUTING_OPTION.by_layer_transmissivity. We could choose an even more lightweight option here, as at_elevation always allocates to a single layer, so no distribution is required. I think to be safe, I want to avoid using by_corrected_transmissivity, as I'm not sure yet whether the correction could result in nasty edge cases for single layers and is more computationally intensive. On the other hand, if a user sets ALLOCATION_OPTION.first_active_to_elevation and forgets to set the conductance distrubtion option, having the simplest distribution method probably yields bad results. So I think for now DISTRIBUTING_OPTION.by_layer_transmissivity is the optimal choice.