I agree with Galina that growing potatoes from seed is an enjoyable exploration and you might well be experimenting for a few years with the small tubers you get this year. I grew potatoes from seed in 2020 (and again this year from Galina’s seed like you) and I’m still taste testing and narrowing down what was produced that year. I had 40+ varieties the first year and have narrowed down to about ten now. Of course what you grow on depends a lot on what space you can give them.
To go to your original question, Juliev, I would narrow down to one per cell at some point. If you’re hoping for inky potatoes as in the images on the Airtable base and earlier on this thread, I would narrow down to the ones with darkest stems and leaves but you might want to go for a range. I think potting on after a while before finally planting them out is definitely a good idea so that you’re planting out reasonably strong plants. You can bury them quite deep if they get a bit leggy and that helps to strengthen them too. I love seeing tiny potatoes developing in the pot before planting out! You might find this thread helpful and interesting when I asked similar questions and got advice on early stages in 2020.
https://www.growingfoodsavingseeds.co.uk/forum/main-forum/potatoes/2039-growing-potatoes-from-true-potato-seeds-tpsBut I hope you get lots of fun out of them and that Galina and I haven’t complicated matters too much with our enthusiasm! They’re good survivors with a will to grow, even though they look delicate in the early stages.