with a physical sim, a Pin is essential to stop removal and abuse. However if you have a physical and pin set, when you reboot the phone it will not get any further than the input sim pin display. So if you have auto reboot set, the phone, if you don't realise it has rebooted, will be just a paper weight, until you pick it up and deal with it.
With an eSim, there is no need for a sim pin, the eSim inside the phone cannot be removed and is protected by the device security pin, fingerprint sensor etc. When the phone reboots it boots up to a device connected to cellular networks etc..
Either way works and is secure, its just which way works for you.