Reddit mentions of Kuretake Zig FUDEBIYORI 12 Colors Set, AP-Certified, Odourless, Xylene Free, Flexible Hard Brush tip, Effective for Both Details and Larger Spaces, Portable, Professional Quality, Made in Japan

A little late to the game, but I have a couple of cents on this topic as well. I own Tombows, the Faber Castell's mentioned below, as well as Pentel Sign Touch Pens, and Kuretake Fudes. I think a lot of the commenters hit the nail on the head re: Tombows. They can be tough to use and hard to control transitions from thick to thin lines. In my experience, this has less to do with the flexibility of the nib and more about the type of head the pen uses. Tombows have a pretty large fiber brush head, and it's not as "springy" as some other pens. This means when you let back on the pressure, you have to really gauge how much pressure you need to reduce to get a thinner line. A lot of pens with a smaller head, especially felt tipped pens, will be a lot more forgiving in terms of pressure variation.

If you do want to get some smaller pens, the FC are decent. They have fantastic color transfer, but I feel like they're scratchier than some of the other options that I have, and also a tad bit more expensive. I really like the Pentel Fude Touch Sign Pens. The head is a tiny bit smaller than the FC pens, so you won't be able to get quite as thick of a downstroke. If you want something more comparable in size to the FCs, Kuretake Fudebiyoris are pretty similar and also writes a bit smoother.

That said, I think it also depends on what you're going for. If you want consistent lettering early on, a felt tip pen with a smaller nib is your best bet. However, because they're so much easier to control, I find that if I use those exclusively for a while, the quality of my lettering deteriorates. Tombows force you to really learn to control your pressure. If your goal is to perfect lettering with all types of pens (felt, brush, watercolor, etc) and with all sorts of nib sizes, I think using Tombows to practice with is the best option.

I've tried a lot of the pens out there. When I was starting out, stiffer pens like the pentel fude pens, Kuretake Fudegokochi, Zebra Fude, or some of the finer tombow were much easier to control. Later I branched out to larger tips like Ecoline, the Tombow dual-tips and the Kuretake Fudebiyori (and a bunch of other random pen types!) but those smaller, stiffer pens remain my recommendation for beginners.