My impression is that dis-economies of scale in fission reactors (safety systems, low-volume manufacturing & construction, local grid management, etc.) are severe enough that neigh-all more-recent proposed designs are for far smaller reactors than the older generation (~1GW per reactor).
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Small Modular Reactors (SMR) are currently the darlings of the nuclear world. They promise cost reduction through mass production in factories rather than on site, smaller size enabling simpler passive emergency cooling, hypothetically simpler licensing through something like type certificates used for, say, airliners rather than starting from scratch for each reactor, etc etc.
This all sounds promising, and it's certainly worth investigating further, however for actual reactors that have been built and operated, cost reduction through increasing the size has been one of the very few approaches that has been empirically demonstrated to work.
The reactors can be small, the plant has to be big to have economies of scale, right?
Not necessarily - one of the proposed use cases for SVBR-100, soviet/russian SMR design, back in 1995 was to provide small power plant distributed to cities or industrial areas, providing 100MWe power or combined heating and electricity. They would compete directly with still common metropolitan power plants, especially CHP in cities with municipal heating.
One of the main issues of the design was that we simply do not produce enough bismuth for the lead-bismuth coolant, and lead-only variant was iirc more problematic due to higher operating temperature. The lead-bismuth design was tested for mnay years as submarine reactor.
Also, under neutron radiation bismuth transmutes into polonium, which is somewhat nasty to deal with.
Most current research on lead-cooled reactors use pure lead. The downside, as you say, is higher melting temperature.
Russian research actually found polonium to be a net benefit!
Namely, the short half-life and the fact that it undergoes alpha decay into lead meant that a) it was very easy to detect leaks b) cleanup was also easier. Also, the rate of polonium production turned out to be pretty low.
The bigger issue is that Bismuth production would be utterly, completely drained by mass production of SVBR-style reactors.
Sure, even if all the previously mentioned SMR advantages would turn out to be true, it would still make sense to place multiple SMR's at the same site in order to take advantage of common grid connections, security, etc.
IIRC Nuscale is designing for up to 12 of their 60 MW reactors in the same plant.
Note that "up to 12" x 60MW = up to 720MW. That is smaller than a single "big, old" 1,000MW reactor.