To the OP and the others who have gone between running and rowing:
A few things that struck me between college running and rowing:
1) rowers train more at less intensity. I went from singles to triples. They can get away with it (less gravity/intensity = lower injury risk), also way more strength training. I still had a stressie though, a rib stressie with a cold is hell btw.
2) cycling everywhere is a must, no worries about 'saving the legs'
(Not surprised rowers transition into successful cyclists- an aerobic beast is an aerobic beast - see Jason Osbourne, also lots of Aussie rower to cyclists... )
3) body image (especially on the women's side!) I always felt like a giant on the xc/track team, the only runner who couldn't fit into xxs/xs clothes (I'm 5'9 / 130, not 5'1 / 100). I didn't have any of those worries in rowing, it was a much more positive experience just focusing on performance and not size (this was a few decades ago, I understand running has improved a lot since).
4) Indoor 2k Erg tests remind me of running indoor miles in badly heated indoor tracks and tower running. All out efforts in bad air giving you a few days of 'track hack' (air quality pending).
5) rowers throw better parties. Not as crazy as swimming, so don't get too worried.
I'm finding imho learning how to move more effectively (regardless of sport) is key to maximising fitness. If you never teach your body how to move quickly and efficiently in your sport, it will be difficult to get better results. In my case as a tall old lady - it's weight training and pelvic floor pt to keep my form for running, but for guys it will be a different program (don't neglect the posterior chain). Also from rowing to running you will need to strengthen your lower legs/feet more too to deal with the increased gravity/load (unless you enjoy foot/Achilles injuries - swimmers struggle with this when they switch to running too).