Not sure about what they “should” be, but I know what I’d like them to be for my (mostly medieval-ish) campaigns. My ideal levels of techs are all over the place: I don’t mind anachronism when compared to real-life eras. In true Tolkien style, technology levels are relatively static, with efforts of industrialisation stunted by the relative ease with which the same results can be accomplished with magic.
Hygiene - I prefer modern understanding of hygiene, not going into the specific knowledge of viruses and whatnot, but enough to keep the population clean and (relatively) healthy, and birthing relatively safe.
Metallurgy - Smiths are capable of creating high-quality steal to forge 16th century weaponry and full plate armour, but mastery of metallurgy is not equal across the world. Much depends on specific mineral deposits and closely-guarded guild secrets. A lot of my « magical » weapons are just that: high-quality steal and workmanship. Rapiers are just a weapon stat: light swords made with good steal made for 1-handed use but without the 17th century aesthetic.
Mechanical Engineering - Simple machines such as block-and-tackle and basic gear mechanisms are well known and used by artisans and peasantry alike, even among archaic humanoid civilisations. Basic water pumps exist but complex hydraulic mechanisms don’t (although Dwarves are more advanced in that domain). Engines and self-propelled vehicles are inexistant with the exception of sail-boats, with the most advanced seagoing civilisation reaching early age-of-sails technology. Mills are about the most advanced, widely used mechanical structures.
Civil Engineering - Absence of concrete limits the scope of constructions, with magic sometimes used as a replacement to create lasting aqueducts and other “marvels” of engineering equivalent to Roman constructions.
Optics - high-quality glass allows for a 19th century prescription glasses, telescopes, lighthouse lenses etc. Most windows feature glass panes, even in smaller villages.
Agriculture - Still heavily dependant on manual labour but with a high yield, allowing the most advanced regions to achieve a 2:1 or even 1:1 rural/urban ratio with magical help and fantasy beasts of burden etc. This is often a big change to classical D&D settings that aren’t even remotely close to that.
Cannons and Firearms - Doesn’t exist, just because I don’t want it to. Historically, firearms and medieval combat coexisted for centuries but here they don’t.
Politics - Mostly feudal structure without the excess of aristocracy and much more flexible social mobility. Rural areas are owned by local lords and ladies, with peasantry closer to employees than serfs. Judicial system is not separated and the lords still hold judicial, legislative and executive powers through a complex systems of vassalship and legislative charts. Sometimes, an organization (such as the Lords Alliance in north-west Forgotten Realms) takes lieu of a king/emperor, or a local lord.
I could go on, but these are the basics. Then we switch to another campaign in Eberron and many things change…
