> I guess this is something that is better changed to 20000 ?

Best value is highly depends on nature of your application. 20000 is
just a default which you can use in absence of more educated estimation.
Auto-sweep interval must be surely bigger than maximal number of
simultaneously running transactions. Say, 2-3 times bigger.
If it's value is lower than max number of parallel transactions,
sweep will be run in vain, degrading performance. If much bigger,
stalled transaction won't be detected for longer time, which also have
negative performance impact (though much lesser) because of bigger
amount of record versions (in the case of stalled transaction only).

SY, SD.