I left all of this to defaults I think. My server.properties contains
maxTextLength=50000
cacheSize=3000
# 1. If you use one or more of English, French, German, Spanish, download ngram data from
# http://languagetool.org/download/ngram-data/ (English: en, French: fr, German: de, Spanish: es)
# 2. Unzip the ngram data files. If you have downloaded English and German, the content of this
# directory would be sub directories named „de“ and „en“.
#languageModel=/home/languagetool/ngram-data
pipelineCaching=true
maxPipelinePoolSize=500
pipelineExpireTimeInSeconds=3600
pipelinePrewarming=true
# maxCheckThreads=6 and maxWorkQueueSize=100 are good values for a server
# with 8 cores. For more cores, increase these values accordingly, e.g. double the number for
# 16 instead of 8 cores.
maxCheckThreads=3
maxWorkQueueSize=50