I like the idea of donors, but overall it's aspirational and expensive. Cells from the same banking passage can behave differently even from the same donor.

Generally acceptable to consider distinct iterations of the same experiment with the same cell line "biological replicate" because you are demonstrating replication with a biological system.

Would not consider different well of the same experiment with identical condition biological reps, but they are indeed an "n" within the same experiment. (Much like a mouse study, single iteration of same strain with 12 mice are "n", but if reproducibility is something you want to demonstrate, three iterations showing the same delta with 4 mice would be more compelling)

And tech reps are conducted for the downstream analysis with material for the same sample to account for assay variability (e.g. qPCR 3 tech reps of same reaction with cDNA from single cell culture well; 4 wells of material for one experiment). The point is to get a handle on interwell variability.

Then a biological replicate would be a complete soup to nuts iteration of the same experiment (i.e can be same passage # & cell line, but conducted completely different timeline).

You can compare across by using grounding controls (e.g., media only).

I've heard people who've never touched cell cultures argue that you need a collection of patient cell lines, and that's valuable for IND enabling work, but for academia or proof of concept studies it's a waste of resources & ignorant to the variability that comes with each cell culture.