There are a sea of different Kensington Hubs as Thunderbolt 4 is coming out and it's pretty hard to figure out what to use for what, but if you have:

1. Older MacBook's with Thunderbolt 3
2. Want to get new M1 MacBooks with Thunderbolt 4, but which are currently limited to a single monitor
3. Be ready for the upcoming M1 MacBook Pros that are rumored for this fall

Then, what's a good dock to get. Certainly you could get an older Thunderbolt 3 dock, but ideally you if you are spending $400, you want something that is going to be future proof. Here are some suggestions: 1. Kensington SD5700T Thunderbolt 4 Docking Station (K35175NA). This is hard to get at Amazon for$370, but it is Thunderbolt 4 with dual 4K 60Hz monitors or a single 8K 30Hz. Then for Windows machines with HBR3 DisplayPort 1.3/1.4 (32Gbps total, 26Gbps Video) or HBR2 used for DisplayPort 1.2, you get dual 4K@30Hz or single at 4K@60 and then for HBR2, you get single 4K@30Hz (that's what an older MacBook Pro 2016/17 supports). The nice thing is you get a 180W power supply, so 90W to your laptop and 15W each to the downstream Thunderbolt 4 devices.
2. Kensington SD4780P Dual 4K Hybrid Thunderbolt 3 Docking Station (K33620NA) for M1 MacBook Multimonitor. For \$300 at Amazon, this thing somehow gets you dual 4K displays as well as 100 Watt power delivery to your Mac and you also get USB-C and USB-A ports. I can't tell how it works, but there is no mention of Thunderbolt anywhere, but it looks like it has two DisplayPort and two HDMI connections, but I'm confused about what the connection to the Mac is actually running. But the data-sheet suggests it is connecting via USB C, but I don't see how it can do that and support the full USB 3.2 standard at 10Gbps, but the Amazon site says that it is actually Thunderbolt 3 which makes some sense. It has a hack that allows dual monitor mode with an M1 Macbook, it sounds this has to do with support DisplayLink.
3. Kensington SD5600T Thunderbolt 3 for Windows. (K34009US). This is recommended fo windows machines, but it is Thunderbolt 3 so 0Tbps with 10Gbps for USB-c and then you get dual 4K@60Hz