It all comes down to your comfort zone. My whole family had Covid months back and the moderna Vaccine. where we live when you donate blood they give you free antibody test's and our whole family had the Covid and the vaccine antibody. We are also going to mask up 2 weeks prior to our vacation just to be sure. As long as the countries do not shut down or the cruise ships cancel our cruise, I am not going to allow this pandemic to dictate my vacation.... I am done living in fear of this new Unvaccinated Pandemic.... I AM DONE.....
It usually works very smoothly. The European cruise lines, MSC and Costa, sometimes have passengers boarding in each of four or five ports and they have it down to a fine art.
The activities being in the "wrong" order is the main oddity. The only other thing that makes you notice it is when, half way through your cruise, you see other passengers luggage out in the hall and you can smile and think to yourself, not me - I've got another 3 days. I have also heard, but have no personal experience, that Royal's cruise planner and app don't handle interporting very well so there may be some difficulties in booking excursions and stuff ahead of time.
The really good thing about it is the convenience of the different departure ports for cruisers coming from different places. For us, for example, travelling from southern Portugal, Barcelona is much more convenient than Rome.