I wouldn't worry about the value difference too much but more the consistency. If you need 75 degrees on the edge then keep dialing up the temp until you get it.
It's most likely only going to affect large prints at the end of the day.
Your printer will measure the bed from a single location so moving your IR sensor will vary across the bed. If your using a custom firmware I'm sure you could set this as an offset assuming your IR thermometer is accurate ;)
Heat of the bed will be the warmest point and the periphery cooler (just like your body temp)
A Thunderbolt cable will handle the required bandwidth from the dock to the laptop.
Your phone, do you expect to pass data via the phone and your laptop (eg photos/videos?) If you do then a USB 3.2 10 Gbps cable would be the most you would need (€25), costs may stear you towards a simple charging cable something around 60w (€10) would be ample BUT you phone may not fast charge due to Samsung's charging preference.
HDMI 2.1 would be ample for a your monitor (4k resolution at 120fps) and the cost difference between this (€13) and 2.0 (€10) is minimal nowerdays
Ethernet is easy, CAT5e in the colour/length of your choice would supply the potential max 2.5gb Ethernet port you have (€8 for 10meters). Higher the CAT rating the more costly the cable.
Additional Thunderbolt ports would be best used/reserved for high-speed external storage or even a gaming GPU.
The fact your asking about these items shows you should be pretty much covered for the next few years of 'fitire proofing'