MSI Bravo 15 C7VFK-431US 15.6" Gaming Laptop Computer - Aluminum Black; AMD Ryzen 7 7735HS 3.2GHz Processor; NVIDIA - Micro Center $750

what's the wattage of the 4060?

This is a decent (though not exceptional) deal, the battery size, the processor, and especially the screen drag it down quite a bit. At $750 this is the cheapest I've seen a new laptop with an rtx 4060 and ddr5 ram. Best buy is notoriously ymmv when it comes to price matching microcenter, so I wouldn't count on it. Also, @ SupersonicX, the best buy link in your original post takes me to a different version of this laptop with the 7940hs processor instead of the 7735hs processor.

There are three primary downsides to this laptop.
The first is the 53.5whr battery. This means that this laptop will have quite poor battery life even amongst gaming laptops, which are already notorious for having terrible battery life.
The second downside is the r7 7735hs cpu, which is not a current gen zen 4 cpu. Instead it uses the last gen zen 3+ architecture, being a modest upgrade in performance to the previous gen r7 6800h while supporting relatively few newer features such as ddr5 (only up to ddr5 4800) and usb4 (the cpu has the capability, but this laptop doesn't have usb4). It has the last gen rdna2 radeon 680m igpu, which is significantly inferior to the current gen rdna3 radeon 780m igpu. Additionally, as a refreshed previous gen architecture, certain features such as higher speed ddr5 support, avx512 support, integrated npu, etc. are non-existent compared to zen 4 phoenix cpus. Power efficiency is also worse. Even though the last gen cpu is somewhat disappointing, it is unlikely to hold back the rtx 4060 in gaming, and should be entirely sufficient for a gaming laptop of this price tier.
Lastly, and by far the most major downside, the screen in this laptop is quite poor quality. According to reviews I've read the panel in this laptop is the Innolux N156HRA-EA1 (CMN1521). While a 1080p 144hz ips display would be perfectly acceptable for a gaming laptop of this tier as long as it had decent brightness and color gamut, the screen in this laptop is only 250 nits with 45% ntsc coverage (similar to 62% srgb coverage). This means the display is not only rather dim, it is severely deficient in capability to display the most limited, basic, and widely used color gamut in existence. Colors will appear extremely washed out on this screen. Realistically speaking, any laptop over $600 should have a 300nit 100% srgb (72% ntsc) screen at minimum, but manufacturers would rather save $10 and neuter their laptop.

The mobile rtx 4060 is the cheapest current gen nvidia mobile gpu that has 8gb of vram, which is a crucial threshold. The next step up, the mobile rtx 4070, is around 20% faster in gaming, while having the same amount of vram. In most respects the mobile rtx 4060 is the value sweetspot, since getting a laptop with a mobile 4070 would usually be ~$300 more. The mobile rtx 4080 is massively superior in terms of performance, but laptops with the 4080 tend to be at absolute minimum $1600. The rtx 4060 in this laptop only has a tgp of 105w, meaning it is not a full power variant. However, performance scaling in gaming for the mobile 4060 stops at 100w, so you don't actually lose any performance with the 105w tgp.

This laptop has two user accessible ram slots (occupied by 2x 8gb ddr5 5200 260-pin SO-DIMM ram sticks), and officially supports up to 64gb. It has two pcie gen 4 m.2 2280 slots (one occupied by the 1tb ssd).

Ultimately, at $750 this laptop with an acceptable processor, a functionally full power rtx 4060, 16gb of ddr5 ram, and a 1tb ssd is a decent value. However, the small battery, functionally last gen cpu, and poor quality screen keep it from being a truly fantastic deal. If you need a gaming laptop right now this wouldn't be a bad purchase, but if you can I'd personally recommend waiting for another deal of similar caliber to the $800 g15 to reappear (the deal linked below was originally $800, but it got changed to $850 after a day): https://slickdeals.net/f/17396106-dell-g15-laptop-15-6-1080p-165hz-ryzen-7-7840hs-rtx-4060-16gb-ram-512gb-ssd-850-free-shipping

I appreciate your insight. Quick question: if my son uses an external monitor, are the screen concerns moot?

The laptop's screen is only a concern so long as you are actually using said screen. So yes, if you're exclusively using an external monitor, the poor quality of the screen included in this laptop is irrelevant. As a side note, the hdmi port on this laptop is hdmi 2.1, so it supports vrr/g-sync assuming the external monitor you wish to connect has a hdmi 2.1 port. However, if your external monitor doesn't have an hdmi 2.1 port, you'd be better served connecting it using the usb c port of the laptop in displayport alt mode.
Also, presumably if you're using an external monitor (unless it's a portable monitor), you'll also have the laptop plugged in, so the small battery isn't a concern either.