Thanks for the review!
The way reactive mode currently works should, I think, do what you're saying. Currently it reduces the view distance until the TPS rises above the limit you set in the config, so if your TPS is 16 your view distance is going to be reduced more than if it was 18, since there's more ground to make up.
The trim-outliers-to-within setting is to do with the way TPS is calculated. The plugin records how long each tick took and looks at the average tick time over some period. If it records a tick that takes more than trim-outliers-to-within per cent of the average tick time, it treats it as though that tick took exactly trim-outliers-to-within per cent of the average tick time. This is kind of similar to a truncated mean:
https://en.wikipedia.org/wiki/Truncated_mean
The advantage of measuring TPS in this way is that random, large lag spikes (like garbage collections or world saves) don't end up skewing the results. This is good, because that kind of 'lag' isn't really related to the number of chunks loaded