"Free" Self-custody solution

I'm new to bitcoin and I don't own much yet but I'm fully orange pilled.

I've been thinkering about the best "free" self-custody solution as it doesn't make sense to buy a coldcard to protect a relatively low amount of bitcoin.

I intend to keep it simple as the last thing I want to do is rugging myself with an over complicated custody system.

Right now this is my plan:

1. Generate a 12 words seed on a newly wiped offline device from bluewallet app in a secured folder (Memorize and write down the words - give a copy of the words to a trusted party)

2. Export xPub to my everyday phone to setup a watch only wallet.

3. Use my offline device to sign transactions if I want to spend or transfer sats.

I really feel this setup is safe even for larger amounts. Am I missing something?