@girish the support replied. I did not have the time to look into it, but wanted to share the feedback with you asap:
You are correct, but you can decrease the amount of converter processes by changing maxprocesscount parameter in default.json file:
/etc/onlyoffice/documentserver/default.json
"FileConverter": {
"converter": {
"maxprocesscount": 1,
The default value is "1" but you can change it (to 0.5 or 0.25 for instance) to decrease the number of processes, since maxprocesscount is a multiplier, the number of converter processes will be equal to maxprocesscount * number of CPUs.
Please, do not forget to restart Document Server's services after applying the changes:
supervisorctl restart all