The answer is it depends what threat are you trying to avoid. If you are targeted by a government-level adversary than yes, you should not use a sim card, use a no-credentials private communicators like SimpleX, use public Wi-Fi on Tor etc. Maybe you just want to escape surveillance capitalism? Are you afraid of being hacked? You need to know what you want to achieve here. Regarding your questions:
Wrench8805 setting system time to UTC+0 (and checking time with wrist watches), so apps can't determine my real location (GPS off, VPN Always-on, only Wi-Fi)
No SIM + VPN should hide your location from sites, but someone better confirm this.
Wrench8805 removing SIM from Pixel and using dumbphone for calls (almost always in airplane mode or powered off when not using it)?
Whether it's dumbphone or smartphone when it connects to cellular network it will send your IMSI (sim card identifier) and IMEI (phone identifier) plus your location can be approximated by the distance of to relay tower. Calls and sms are always to be considered compromised. If that is outside of your threat model than some people recommended using a portable modem like MUDI with custom firmware for spoofing IMEI and communicating with E2E encypted app.