What is the default Imperial Power Projection Target game rule in CK3?

AI Only: Extra restrictions on the creation of Empire-Tier Titles will apply only to the AI. (patch 1.20.1.2)

Does changing the Imperial Power Projection Target rule disable achievements?

No: none of its 3 settings carries the flag blocks_achievements in patch 1.20.1.2.

Game rule · Titles & Realm · Tweaks

Imperial Power Projection Target

AI Only · default
Anyone
Player Only

Imperial Power Projection Target is a game rule in Crusader Kings III (Titles & Realm and Tweaks) with 3 settings: AI Only (the default), Anyone and Player Only. None of its settings disables achievements. Patch 1.20.1.2, from game/common/game_rules/00_game_rules.txt.

This section as JSON: /raw/game-rules.json

Quick answers (2)

What is the default Imperial Power Projection Target game rule in CK3?: AI Only: Extra restrictions on the creation of Empire-Tier Titles will apply only to the AI. (patch 1.20.1.2)
Does changing the Imperial Power Projection Target rule disable achievements?: No: none of its 3 settings carries the flag blocks_achievements in patch 1.20.1.2.

3 settings

AI Only
Default
Extra restrictions on the creation of Empire-Tier Titles will apply only to the AI.
The script checks it once, in 1 place
Scripted triggers 1
- rule_title_creation_imperial_power_projection_title_creation_targeting_trigger
Every has_game_rule = title_creation_imperial_power_projection_targeting_ai_only in game/common and game/events, by the top-level object it sits in.
title_creation_imperial_power_projection_targeting_ai_only
Anyone
Extra restrictions on the creation of Empire-Tier Titles will apply only to all Characters.
title_creation_imperial_power_projection_targeting_both
Player Only
Extra restrictions on the creation of Empire-Tier Titles will apply only to players
The script checks it once, in 1 place
Scripted triggers 1
- rule_title_creation_imperial_power_projection_title_creation_targeting_trigger
Every has_game_rule = title_creation_imperial_power_projection_targeting_player_only in game/common and game/events, by the top-level object it sits in.
title_creation_imperial_power_projection_targeting_player_only

Source: game/common/game_rules/00_game_rules.txt line 1531 (key title_creation_imperial_power_projection_targeting), modifiers from game/common/modifiers, names from the English localisation; Crusader Kings III 1.20.1.2.