That’s a broad question, which you were right to spin off into a separate thread – Language learners: What do you do to make sure you are learning cards rather than brute-force repeating them? .
Is that how many you see in Stats, or how many FSRS counts when you optimize this preset?
It doesn’t matter what algorithm you used to study the cards – your retention results are your retention results. (So if these are Stats from your FSRS test-area, that’s not what you want.)
95% is very high to set your DR – higher than necessary for most users for more purposes. But if you have been able to maintain 95% retention over a long period of time (longer than 1 week, look at month/year/all), even while you’ve been down-grading your cards as you have been – then sure, you can try setting 95% for your DR. You should expect a high workload from that.
I’m not sure how you’re getting 96.4% retention, if you’re grading cards Again 15% of the time. Are you comparing information for the same data? That looks like 85% would be a much more appropriate starting place for your DR.
[The rest of the things you narrated aren’t relevant, and screenshots of the actual Stats graphs would have made this go faster. Instead, I just looked at your synced (real) collection myself.]
There isn’t a lot of difference between those sets of parameters. I don’t think you need to be so picky about what cards you include/exclude from your preset. For instance, there’s nothing wrong with using “Grade Now” to start a card, as long as those grades were accurate. And since that’s a small slice of your collection, it won’t skew your parameters far in one direction.
FSRS can deal just fine with some cards being easier than other cards, and with cards being studied when they are overdue.
What that suggests is a lot of those times you were down-grading your cards to Again at the start, you still ended up remembering them just fine. I don’t think that will be a problem in your history/parameters. If you want to compare your sets of parameters to each other, you can use the FSRS Visualizer site you were using above.