Google-sheets – Show only own record to Google Spreadsheet user and hide data from other users

In an arrangement where each of N user's changes propagate to all the other users' screens, that incurs N² propagation costs (network messages, recalculations, and display updates). That grows rapidly as N grows. So if N > 3 you want to avoid it for sure.

A separate sheet per user might avoid most of the updates but the best bet is to use a separate spreadsheet document for each user.

Given that, using a separate Google Account per user might improve performance a bit by avoiding synchronized updates to some shared state (e.g. the user's document list). Also this is the normal case, unlike one account editing docs from many tablets at once, and any optimizations will favor the normal case. You'd have to measure it to be sure, but my semi-informed bet is that you won't notice the performance difference.

Giving each user a separate login account would help with tracking changes, but that might not be worth your setup work.

Idea: If all the columns are uniform within each sheet, that is, if the data is like a simple sequence of records, look into using Google Fusion Tables in place of spreadsheets. Fusion Tables scale up to very large data sets since the rows are independent of each other. You can "publish" columns from one table data to other tables.

Idea: If this is not a temporary application, consider replacing the spreadsheets with a custom implementation as a web app or native Android apps. Even then, it's good to prototype your application with spreadsheets as a way to discover what really matters to your use.

I think you have two choices that would not suit you:

1) Put French into wherever you are importing from.
2) Once the range is imported, break the link (Copy, Paste special, Paste values only) so that deleting Ana in the source no longer causes her to disappear from the imported data.

Both the above can be avoided with a lookup table but to do so would be ‘ugly’ and if imported data is added to, rather than have parts deleted from it, could require a tedious amount of repetition. However it might be acceptable as a workaround.

Import to two different ranges and Copy, Paste special, Paste values only one of those. Add French to the converted version (the one no longer linked) and use that as a lookup table to place French where you would like, by searching for Jacques (and Ana and Peter) by cell reference from the linked version.