Mylink blue tooth did not have this issue with earlier versions of IOS. I used to stream Pandora back in the day with my previous VF and was fine. I know now at startup it can be a pain until the unit settles down and has gone through it's boot up phase.
I havn't spent much time in the car as the misses is driving it daily but everytime I drive it, bluetooth is horrible for the first 5 mins but usually comes good with only a stutter once every 10 minutes or so, which is bareable. Unable to tell with the misses (other than the saturday just gone) because she listens to the radio. No idea how she listens to the verbal diarrhoea of radio hosts and radio adverts.
not sure if the aftermarket heated seats would work well, you need to be mindful that if you wire something wrong it can damage things beyond the module that controls the heated seats.
with the stuttering over bluetooth was the phone anywhere near the mylink screen?
the reason i ask this is the screen module on the mylink puts out a fair bit of emi and it can mess with signals.
something else with bluetooth these days is modern devices attempting to push higher bitrate data over the connection which can cause stuttering(buffering) on older devices.
newer devices have a higher profile of bluetooth ie "bluetooth 5.X" so they can handle the bandwidth but something like the mylink is around the 3 or 4 profile.
poorly optimized apps will not detect the connection profile and adjust the bitrate accordingly or may be blocked from that information due to os restrictions so they just try to use the single bitrate and send it.
the tech in the mylink is over 10 years old now(getting close to 15) so the support for things like older bluetooth is starting to fade which is why newer devices are starting to have issues with mylink.
i cant really comment on the ksmart module and how well it would work for you but on your phone see if you can find an option for lower bitrate or a lower connection profile with bluetooth that might reduce the stuttering.
From the link I posted earlier on the SSForums, my understanding is that wiring would go like this:
Button gets pressed and the head unit sends a signal to the BCM via the CAN network that the switch has been activated. The BCM then tells the head unit to light the up the LEDs (in the switch) and simultanously tells the Heated Seat Module (possibly via CAN) that a heated seat needs to be activated. The heated seat module then sends a PWM signal to the Heating Pads, causing them to heat up. There's probably a whole lot more involved and I would guess there would be thermostat which tells the Heated Seat Module the temp of the pads, so they don't catch fire basically.
Fun tip, if the BCM detects that the car is under high electrical load it will disable the heated seat module (and various other non essential electrical systems.)
These aftermarket heated seat kits are a standalone unit with it's own power and control module, it would be wired in completely seperate from the factory modules and BCM thus shouldn't cause any damage to the original components. The only potential damage I could forsee would be possibly electrically damaging the Factory pads with the incorrect voltages/amps/pwm signal, In which it would probably be wise using the supplied aftermarket heating pads, checking the signal from both the factory and aftermarket pads to make sure they operate the same or Possibly shorting the factory switches again checking if they operate the same factory to aftermarket.
As far as the stuttering, both phones were in the cup holders, passanger seat (being held by the passenger) or in the back seat and not sitting directly on top of/under the head unit, which IMO "shouldn't" be an issue at those distances. Unfortunately neither phone have the support to change the audio sample rate in developer options, so there's no fix there.
As you stated, the tech in mylink is close to 15 years old, hence why I would rather upgrade the unit completely. It will just require some modifications to retain heated seats. If I can get the heated seats wortking the math on the that one $650 for the head unit with the button holes, $100 for factory switches, $70 for a heated seat kit, about $820. . I think it might be worth messaging the ali express link to see if they will supply just the empty facia with button holes or get super handy with a dremel and get the $270 unit and cut the wholes for the buttons and somehow mount/glue them into the facia.