What determines starting TP in Chain Attacks

When starting a chain attack, each character starts with some number of TP. The amount is different for each character, and it's not clear what influences it. Knowing what changes this number could help ensure more powerful or consistent chain attacks.

The initial TP is always a set number during the first chain attack order under normal conditions:
Main character: Noah (30), Mio (25), Eunie (25), Taion (35), Lanz (15), and Sena (15)
Heros: Ethel (25), Valdi (20), Zeon (25), Teach (30), Riku & Manana (15), Gray (35), Isurd (40), Juniper (25), Ashera (15), Alexandria (30), Monica (30), Fiona (15), Triton (10), Ghondor (35), Cammuravi (15), Segiri (20)
Miyabi (15), Nia (15), Melia (35)
There are ways to increase the base TP for the characters, and this is can be done through various means:
Ways to increased the starting base
Equipping the Lost Vanguard skill https://game8.co/games/XenobladeChronicles3/archives/384954 can increase the base TP by 5 at rank 5, and then 7 at rank 10.
Equipping the Soul Hacker skill https://game8.co/games/XenobladeChronicles3/archives/384904 can increase the base TP by 5.
Equipping the https://game8.co/games/XenobladeChronicles3/archives/385375 accessory can increase the base TP by 10.
Ways to increase the TP during chain orders
https://xenoblade.fandom.com/wiki/Teach heroic chain bonus can increase all active characters base TP by 10, including the first chain order
https://xenoblade.fandom.com/wiki/Riku_%26_Manana heroic chain bonus can increase everyone's TP by 7
https://xenoblade.fandom.com/wiki/Miyabi heroic chain bonus can increase Mio's TP, including the first chain order