Okay, let's cover some basics as your note you're "new" to VoIP.
For a switch that supports VLANs, we need some way to separate frames into different VLANs. There are a few ways to do this, the most common being, you assign a port to a VLAN. Frames going in/out that port look just like any other similar port's frames, but the switch logically segregates the frames. For example, frames using ports 5 and 6 in VLAN 10 are not shared/intermingled with frames using ports 15 and 16, if those ports are defined to be in VLAN 20. However, of course, fames using ports 5 and 6, or ports 15 and 16, can be shared/intermingled for ports in the same VLAN. Again, frames going in/out these 4 ports, look "alike".
If you wanted to "share" VLANs 10 and 20 with another switch, keeping those VLANs separated, you might connect port 5 or 6 to another switch's port 10, if port 10 is also defined to be VLAN 10. Likewise, port 15 or 16 might be connected to port 20, on the other switch, if port 20 is defined to be in VLAN 20. Still, you cannot distinguish between VLAN 10 and VLAN 20 frames, looking at just the frames.
Using a port per VLAN to interconnect switches isn't very "nice" as you create more and more VLANs. So, we define a way to tag frames with their VLAN ID, and since frames can now be distinguished they can be sent in/out the same port, which Cisco calls a trunk port. Cisco's trunk ports allow you to work with any one single VLAN's frames without tags, which you configure as the "native" ("native" as its looks the same as any other untagged frame). Basically, the "native" VLAN assigns untagged frames to use a particular VLAN the same as an access port assigns untagged frames to a particular VLAN. The big difference, a trunk port can send other VLANs in/out the same port, as they will be tagged with a VLAN ID.
Basically, most modern VoIP phones have built-in "special/limited" VLAN capable switch.
Above, I mentioned how two switches could share multiple VLANs on the same port if the frames were tagged. In Cisco's trunk implementation, you can also mix a single untagged set of frames, with the other tagged frames, because you configure the switch to assign untagged frames to a particular VLAN.
A VoIP phones, it designed like this too, although it only supports two VLANs, one untagged and one tagged.
Such a phone can interoperate with a Cisco trunk port, also configured to use just one untagged VLAN (native), and one tagged VLAN. Since such a VoIP phone is limited to two VLANs, again, untagged and tagged, Cisco created an option for access ports to support one additional VLAN, tagged, in addition to their already untagged VLAN (this to avoid using a Cisco trunk port, for the same purpose - which, before there were access ports with "voice" VLANs, was how it could be done).
Cisco's implementation "names" the tagged VLAN "voice", because that's generally what it's always used for, but the switch port really doesn't care. All it cares about is that you assigned one VLAN for untagged frames (classical access port - and much like a trunk port's native assignment) and one VLAN for tagged frames (unlike a trunk port, as they, by default, carry all VLANs known on the switch, but can be restricted to just one VLAN).
So, what my prior reference to another thread showed, from a VLAN and frame tagging perspective, an access port defined with a "voice" VLAN is very much like a trunk port using just two VLANs, one of which is "native" or untagged (actually there are other differences too, dealing with "control", but for "our traffic", they don't normally matter).
This is why I mention, VLAN 1, 64, 65, etc., doesn't matter. You determine what your VLANs are, how they are to be used, and, as they use the port, whether frames are tagged for not.
BTW, another way to setup up VoIP phones, is they and your PCs, each, have their own port connections. Sharing a port, like a trunk, vs. one per, between switches, for each VLAN, just reduces edge port requirements.
Further, whether VoIP phones share a port with a PC, or have their own ports, you can have VoIP phones with their own VLAN or they can share a VLAN with PCs.
I.e. you can mix and match shared VLANs vs. separate VLANs for VoIP phones and PCs along with VoIP phones and PCs having separate edge ports vs. sharing an edge port.
As a VoIP phone's built-in "special/limited" VLAN switch (to my knowledge) always uses untagged frames for downstream devices. Further, if the VoIP phone is also using tagged frames (to my knowledge) it always used for the VoIP phone, itself. Again, it's up to you configure your edge port as desired, i.e. whether to use only untagged frames or untagged and tagged, and VLAN assignments for what you're using.
As to VoIP phone "knowing" whether to use tagged frames for themselves, and if so, what the VLAN tags should be, that varies a bit by brand of VoIP phone and/or configuration options on the phone. For example, VoIP phone might use CDP and/or LLDP to determine if edge port is providing a tagged VLAN, and if it does, VoIP phones assumes it's for exclusive use of the phone. Or, phone might be "hard coded" to use a particular VLAN tagged frames. Or, phone might get a DHCP option string which indicates it should use a particular tagged VLAN ID for its traffic.
Hopefully, the above might help you better understand how VoIP phones use untagged or tagged frames.
If you have questions on the above, feel free to post them.
