There are no critical rules that must be followed as to which accessory gets installed on the right vs the left hand accessory ports of a tank tee. However, the upward facing accessory ports on the tank tee are threaded in a way so that certain accessories will only fit in the orientation they are meant for. The nipple and pressure gauge will only fit the 1/4" threaded ports in the top.
Liquid filled gauges must be lower mount model. Otherwise, the glycerin would leak out when they gauge plug is snipped for venting.
In theory, you could use a dry, center-back-mount pressure gauge so that the gauge face is oriented upward for easier viewing. However, dust and debris could accumulate more easily and obscure the gauge face.