Custom index maintenance percentages for a very large table
It really depends on how transactional your tables are. If they are frequently being updated and inserted into, you'll definitely hit the 10%. If you're not hitting the 10% then it's probably not even worth it to lower to 5% because that means your tables are fairly well unfragmented already.
I've personally worked on a very similarly sized database to your example, also SQL Server 2016 standard, on a server that only had 16 GB of RAM. Our database was fairly transactional (adding about 1,000 new records every few minutes) and we were hitting the 10% threshold for reorgs every night. Because the operation was so heavy and took a while, I actually did the opposite and increased the fragmentation threshold for reorgs to 20% for our larger Tables' indexes. This proved a lot better for our business because the different in performance was negligible and it generally allowed for the larger tables to not be reorganized until the weekend.
Worrying about index reorgs, and even more so rebuilds, is on the low end of things to optimize for. Even Brent Ozar says not to worry about it. :)