I only use a TDS meter to make sure my ro/di is working and the filters do not need to be changed.
I would never use a TDS meter to determine if a tank needs a PWC because it will show a high reading just from the food/supplements you add.
For the first 6 months I recommend performing a 10%-15% PWC weekly until your tank stabilizes. After that you can cut it to 10%-15% every other week as long as you don’t overstock/overfeed your tank and your no3 remains below 10 ppm.
Performing PWC is necessary not only to keep your levels balanced but also to replace trace elements your fish/inverts need.