I have to agree with @nestorayuso here. Nobody is using 433MHz for LoRa. If you however do feel that you want to go that way, it defeats the point of using TTN, and you can just as well run your own private network.
868MHz equipment is just as available, if not more available, than 433MHz equipment. Also the antenna size on 868MHz is nicer for small sensors.
I however do not rule out 433MHz at all. It is something that is still on my want-to-do list. The trick is getting a global frequency plan set up that has at least one channel overlap in all regions. Then one can add extra channels per region, which can be dynamically configured into a device at join.
Anyway Im starting out with 434.250 SF12BW125 100% duty cycle/100mW.
That’s not nice of you.
868MHz specifies a 1% duty cycle per device to prevent over-use by a single user. Remember it is a shared resource. SF12 is also overkill. SF7 is normally good enough for most uses. SF12 hardcoded into a device is also not allowed by the LoRaWAN standard. One should start at SF7 and slowly go up until the network tells you you are in reach (Adaptive Data Rate).
Please don’t let me stop you from hobbying around
But sometimes it is just easier keeping to the standards.