The apcsmart driver should recognize (or at the very least, work with) the majority of Smart-UPS models — which includes Smart-UPS, Matrix-UPS and Back-UPS lineups, among few other ones.

Currently, we can roughly divide APC hardware into four groups (note that the division isn’t strict by any means, and the borders between those are pretty fuzzy):

[very] "old" models

These models usually have old APC logo, white color and no programmable EEPROM; you won’t find them listed anywhere on APC’s site either. The support for those will be usually based on driver’s compatibility tables, or if the model (firmware) is not listed in those — the driver will try to follow the very basic subset of features, while still trying to remain useful. Despite "smart" tagname, they often tend to behave in pretty dumb way (see the section below about shutdown behaviour).
Example models:

    Smart-UPS 2000I

    Smart-UPS 900I

"new" models

These models usually come from late 1990s / pre-2009 times. They are often referred to as "3rd. gen". For the most part, they have programmable EEPROM, report supported commands and capabilities, and should work just fine with the apcsmart driver.

"microlink" models

WARNING: These are not natively supported by apcsmart (or as of this writing by apcupsd, for that matter, if you’re wondering). Around 2007, APC (now APC Schneider) decided to go back to its proprietary roots, and all the new models (SMT, SMX, SURTD) use completely different protocol and cables. If you purchased a new APC UPS — that uses cable with RJ45 on the one end, and DB-9 on the other — then you have such model. Your only option to support it through NUT is to purchase a "legacy communications card" —  part #AP9620 (google AP9620 for more details). Or if that’s not an option, rely on official software.
UPDATE:

Later releases of apcupsd claimed support for new APC protocols, so it is worth checking if apcupsd software would work with your device, and apcupsd-ups NUT driver would handle it as part of NUT-managed ecosystem.

Microsol models

Several Microsol serial models sold in Brazil have been rebranded as APC Back-UPS, and the model numbers tend to start with "BZ". If you have one of these "Nobreaks", they will not work with the apcsmart driver — please see the solis(8) driver instead.
Example models:

    Back-UPS BZ1200-BR

    Back-UPS BZ2200BI-BR

Another thing to remember is that Smart protocol is not USB protocol. If you have UPS with both USB and serial ports, then depending on how you connect it, you will need either apcsmart or usbhid-ups driver.