In the context of the Poco F1 (or any other phone that is not the Pixel 1/2/3/3a and XLs for that matter), Pixel Experience is a custom ROM for these reasons:
- Pixel Experience is not a GSI image that we just put in Pocophone. It also has its code based off Lineage with Pixel sources too (and with CAF, Qualcomm-specific code).
- Try flashing MIUI stock straight on top of PE. You'll see lots of errors, simply because the frameworks are different. Stock ROM for Poco is MIUI. You can try checking the Poco out of the box.
- Expounding on the topic, xiaomi.eu is considered a custom ROM because it has system level changes for the removal of ads and Chinese localization (apart from the fact that it is deodexed). If xiaomi.eu is a custom ROM in itself, then by what claim can we say that PE is non-custom?
- Please have a look at this changelog for the CAF version of PE (I think AOSP has it too) : https://github.com/PixelExperience/..._caf_beryllium-9.0-20190505-2106-OFFICIAL.txt
Of course, you might have a different view of what "seems custom", but the vast difference of the PE ROM from the MIUI ROM speaks for itself that it is indeed custom (BTW, there's a high chance that ROMs that require you to flash them through TWRP is custom).
My apologies for a rather harsh attitude earlier. I'm here to inform and respectfully agree or disagree with what I know. Have a good day.
---------- Post added at 07:48 PM ---------- Previous post was at 07:41 PM ----------
Legit concerns. I personally like how Huawei implemented EMUI and OOS on Oneplus. However, I did answer the mere question of the existence of a dark mode, as the Messages and Phone apps on PE is bundled as its default.
I will concede that Android Messaging apps are a mess, whether through their inconsistencies and their UI. But we can only hope for better things.