Achievement for Tactician Mode when changing to custom mode?

[Lord Pigfoot Nosebeggar XVII]

We're currently still finishing the game in tactician mode, but most of the time it is not hard enough. We want to increase the difficulty somewhat using custom mode, since you can now switch over. Will this affect the tactician mode achievement?

[Boombastic]

Yes. You cannot change the difficulty mode.

For the achievement you have to have chosen Tachtician mode in the begining of the game and keep it like this untill the end.

At least this is what I read in the Trophy guides and also how I did it.

https://psnprofiles.com/guide/17598-baldurs-gate-iii-trophy-guide#57-critical-hit

This trophy requires playing the game on its highest difficulty: tactician. Doing so requires starting a fresh file on the hardest difficulty and never changing it. What makes this difficulty so challenging is that it increases enemy health pools and ability scores, with some enemies gaining additional abilities that may hinder you. Not only that, but the cost of long rests has been doubled, now requiring 80 supplies instead of 40. As such, enemies will be more difficult to fell as they find it all the easier to harm you, all while you'll be hurting for supplies to take much needed rests.

Due to the nature of this game, there is no one "best way" to tackle this difficulty as there are a multitude of ways to tackle the story, each which come with their own consequences. Nor is there technically a best party to have as every character can be specced (or respecced) in any way the player desires. However, there are plenty of ways to help make this difficulty even a bit easier.

[Lord Pigfoot Nosebeggar XVII]

That's a shame, we're currently just easily breezing through. I'm going to choose custom right away on my single player save after we finish.