Biggest benefit, but theoretically hardest to achieve, is boron fusion, which is nonradioactive. Since the energy is carried away in charged particles instead of neutrons, you don't need a steam cycle.

Focus fusion would be a small boron fusion device, producing 5MW per reactor at a tenth the price of coal. Potential drawbacks: the energy gain is a bit marginal so you have to also capture x-rays, and erosion of the electrodes could be a problem. But a 5MW plant should only cost half a million or so.

Picosecond laser would also do boron fusion (which in that design is only ten times harder than D-T), but with a 10,000x energy gain, divided by the one percent efficiency of the laser. It's projected to produce power as cheaply as focus fusion.

Tri-Alpha supposedly could achieve boron fusion but they've been very tight-lipped about the whole thing. They've gotten close to $100 million in venture capital though, including from Paul Allen.

Polywell, if it works, could do D-T fusion in a 2-meter sphere, or boron fusion in a 3-meter. I've seen relatively high projected costs, though that may be for D-T. If you're a scifi fan, this was invented by the guy who came up with Bussard ramjets. He was also a big tokamak guy, before he gave up on them.

Levitated dipole sorta turns tokamaks inside-out, with the plasma contained around the outside of a solid levitating torus. This seems to solve some plasma instabilities that tokamaks struggle with. They say it would be ideal for D-D fusion.

Deuterium (for D-D) and boron are readily available in large quantities relative to what we'd need. D-T needs tritium, which would have to be made by bombarding lithium with the neutrons from the fusion reaction. This would limit how fast we could roll out the reactors. D-D and D-T would both require steam turbines. Most people focus on D-T since it has the least stringent requirements, and the rest of these are D-T.

General Fusion uses a vat of molten lead and lithium, spinning to open a channel down the middle. A plasma ball is shot in from each end, then 200 steam-driven pistons slam into the container, making an acoustic shock wave that compresses the D-T plasma. The neutrons hit the lithium for tritium, heat the lead, and it all drives the steam turbine, with some steam diverted to drive the pistons. Jeff Bezos is a big investor in this one. Right now they've got the pistons working with the tight timing they need, and a prototype with a dozen pistons or so.

NIF says they're farthest along the development path, they're leveraging big advances in lasers, and with their LIFE development they're already working with thirty or so commercial suppliers to put together a practical reactor design with as much off-the-shelf equipment as possible. They don't need as much tritium inventory to start up as tokamaks, and think they can be competitive with fossil fuels. They've been talking 2020 or so for a demo reactor, but they also thought they'd manage ignition this year, and a recent DOE report said it'll be another couple years.

Helion targets a middle ground between tokamaks and NIF, in terms of temperature and density, which they think will be easier. They need $20 million for a full-size reactor, already built a 1/3-scale test unit. They're also working with NASA on a fusion rocket design.

Tokamak (like ITER) seems to be on a solid path to net power, but it's such a huge, complicated, expensive device that it's hard to imagine it being economical, and they're talking about a thirty year timeframe at best.