Delete Original OSX Install Partition / Make existing Second Partition with New OSX install as MAIN

Hi. Having brought home the iMac from the office some months ago , that was a single partition with Catalina 10.15.7 installed, I decided I needed my own fresh install and made a second partition to install a new copy OSX to use as personal computer for audio work etc. All working fine to date.

I'm now in the position that I want to remove the original office installation/partition altogether and reclaim the HD space, and continue with the second install as the main going forward.

Is this going to be simple? or are there some pitfalls ahead? Is it really as easy as erasing with Disk Utility?

in the screenshot below it is imac_1_hd and imac_hd_Data that I am considering removing.

Once I was set up on the new install I did initiate a regular time machine back up to an external drive, so I do have that if needed. However, what I noticed is that I was unable to entirely exclude the original install partition from the TM back up options.

It will let me select the imac_hd_Data with no issue. But imac_1_hd does not seem to be allowed for exclusion (the exclude button is greyed out), which makes me think there is possibly some linked systems in place that are going to get screwed up if I manage to erase it. Or at the very least, if I were ever to attempt a recovery from this time machine back up I will end up with this original partition back in place.

I'd appreciate and tips here before making such a bold move.

Thanks!