I've been using data-only SIMs (and now eSIMS) since 2015. Bria voip client with voip.ms providing DIDs. Works wonderfully well and I can highly recommend going voip-only if you can.

The thing holding me back from going iPad Mini instead of iPhone was Apple Watch needs the iPhone (for some reason you can't use an iPad or Mac). Not an issue anymore. But now I rely on the amazing 16 Pro camera (with Halide shooting RAW) to mostly replace my mirrorless RX1, so yet another reason to stay iPhone.