Looking at the
Adobe system requirements for Lightroom Classic, for optimal performance you’ll what to aim for the Recommended level, not the Minimum level. That’s definitely possible with a new MacBook Pro.
The base 16" MacBook Pro ($2399) should run Lightroom Classic well as is; adding a few hundred dollars worth of upgrades might keep it current for longer. But the one thing that is not necessary is to max it out; that would be overkill for Lightroom Classic. If portability is more important than top performance, you might consider the 13". (Don’t get a 15", because the 2019 16" fixes a lot of what people complained about with the 2016–2019 15".)
If you want more details…
CPU: The 6 cores in the 16" base model CPU are already approaching the limit of how many cores Lightroom Classic can use productively, so there isn’t much need to upgrade the CPU unless your budget is generous. If you are looking at the 13", get a 2.4GHz CPU, not a 1.7GHz.
RAM: Lightroom Classic performs best with 12GB RAM or more, and the Mac system needs a few GB too, so 16GB RAM is the practical starting point. If you want to edit or merge large images, or run other memory-hungry applications at the same time such as Photoshop, get 32GB RAM instead which is only possible on the 16". There is no need to get 64GB RAM for the 16" unless you have a good reason other than Lightroom Classic.
Storage: Mac internal storage is so expensive in part because they use very fast storage chips which are several times faster than an SSD in a 2013 MacBook Pro. Get an amount of internal storage you can reasonably afford (mine has 1TB), making sure to allow for plenty of free space for caches, previews, etc. Then consider putting your main photo storage on a compact but fast external SSD such as a Samsung T5. I'd like to move my 100,000+ photos from hard drives to a single 4TB external SSD, but external SSDs of that size aren’t common. So I’m thinking about buying a 4TB internal SSD like those by
Samsung or
SanDisk, and putting it into a very portable
USB 3.1 Gen 2 enclosure for speedy access from a MacBook Pro. But for now I’ve decided to wait for the street price of a 4TB SSD to come down from the current $450.
Graphics: The discrete graphics in the base 16" MacBook Pro can provide Lightroom Classic with much better GPU acceleration than the integrated graphics in any of the 13" models. For just Lightroom Classic, the graphics in the base 16" model are fine, especially if you are not plugging in external displays. Some power users say the $200 upgrade to 8GB of graphics RAM is worth it. But remember that in Lightroom Classic, only the Develop module uses graphics acceleration…everything else depends on CPU performance.
I moved from a 2011 15" MacBook Pro (i7 CPU) to a 2018 13" MacBook Pro (i5 CPU). On paper, the new one looks worse: Lower CPU level, no discrete graphics, same amount of RAM (16GB). But CPUs advanced so much in 7 years that the 2018 13" soundly beats the 2011 15" in Lightroom Classic performance, with better battery life, and a lot less fan noise.