lalitik, I'm old enough that I began buying LPs after stereo had been introduced but while mono versions of most recording were still being released. I didn't yet have a stereo system so I have many older mono LPs. As a result I had similar questions to yours.
As a result I also considered a two arm set up, one with a mono cartridge. Then I became concerned about EQ after learning not all labels accepted the RIAA after it was established. I don't claim expertise but here are my conclusions.
It comes down to when the given mono records were produced. For the now many reissues of classic/popular mono recordings, a quality stereo cartridge played through a mono circuit in a phono stage will be good. That is because apparently mono cutter heads are no longer available so the mono reissues were cut with stereo heads. Matching groove width is important and this satisfies that.
For older original mono LPs then a mono cartridge with proper stylus size and lateral only pickup (less noise) should perform best. Along with a mono playback stage.
Regarding EQ, I realized my mono LPs were issued beginning in the late '50s and are all US pressings. So they are all RIAA, thus eliminating my need for adjustable EQ.
In my old age with the desire to simplify as much as possible I settled for a single arm with interchangeable head shells to accommodate both stereo and mono cartridges, along with a mono switch.