Here's a linux pp table editor that also seems to support more options (such as
raising the power cap) than OverDriveNTool:
https://github.com/amezin/powerplay-table-editor

I will note that you might still see raised voltages if you do a too aggressive
overclock/undervolt with modded PP tables, but it seems to only overvolt as
much as is needed (say 975mv -> 1.05V) if you set a too high clock, rather than
jumping to the maximum possible voltage that you see by editing
pp_od_clk_voltage.