Is it biwiring or biamping if using two separate speaker posts of a single amp?

Any speaker may benefit from biamping, but not necessarily from biwiring.

Biamping means separate power supplies so the amp(s) are a lot less likely to get driven into clipping.

Somebody else will have to explain the mechanism behind biwiring as it doesn't seem to make sense.

You will either need 2 amps, or a "multiple" amp - I use a Sunfire Cinema Seven which has a very special power supply.

Since your Creel 5350SE is capable of driving two sets of speakers, through it's A or B outputs, if your were to hook up both A&B outputs to one set of speakers, this would be considered bi-amping.

John (Jmcgrogan2), no, for only the second time in recorded history I must disagree with you. Various statements in the manual for the amp in question will confirm that as I would have expected both the A and B outputs for each channel are driven by the same output stage. And the single output stage for each channel is simply routed to either the A terminals or the B terminals or both or neither , depending on the setting of a front panel switch.

Connecting one of those amplifier terminals to the high frequency section of the speaker and the other to the low frequency section of the speaker therefore amounts to biwiring. The only differences between that and the most commonly seen forms of biwiring are the insertion of the switch into the signal path, and the provision of two pairs of output terminals that are paralleled (connected together) when A + B is selected. Biamping would mean that either separate amplifier output stages or separate amplifiers drive the low frequency and high frequency inputs of the speaker.

To the OP, if you search past threads that have appeared here on biwiring, as might be expected you’ll find no consensus. Some report improved sonics to varying degrees, some report worse sonics, and some report no difference.

Regards,
-- Al

"Since your Creel 5350SE is capable of driving two sets of speakers, through it's A or B outputs, if your were to hook up both A&B outputs to one set of speakers, this would be considered bi-amping."

Sorry, that is incorrect. A & B outputs are just 2 connections to a single amplifier. Bi-amping requires 2 separate amplifier channels to each speaker. So either 2 stereo amps, 4 mono blocks, or a multi-channel amp with at least 4 channels is necessary for bi-amping a 2 channel system.

"If I connect the Hi to A and Lo to B, is that biamping or biwiring?"

That is bi-wiring. Also, using A or A&B on a single pair of speakers has no appreciable effect on amplifier output.