Voadam
Legend
I have played and DM'd a bunch of D&D with one player.
If they run two characters it gets less personal and more 3rd person perspective, my tastes run to preferring more first person single character immersion.
While NPCs can make it more like a normal party for capabilities and action economy, I find having a pet generally works better so the PC does not feel others are doing the work for them or bailing them out. An animal companion/familiar/eidolon whatever feels more like part of your character and less like a DM PC.
Doing a single person thing with no pets can be super rewarding though as it is all you. Being an actual thief doing a burglary is a lot easier to feel like a burglary for a single rogue than for a group with a paladin and a druid and a monk. As a DM you can really tune the adventure to the character and their character concept instead of to an independent story line for a group as you don't need to worry about other PCs' spotlight time or keeping the action appropriate for a whole group.
For D&D since there are generally four niches (warrior, skill person, healer, utility magic) multiclassing or hybrid classes work fairly well for a solo person even if they are weaker than a maxed out single class specialist would be. Playing a 3e wizard who dipped ranger costs a caster level and your highest level spells half the time, but those extra hp and the ability to use weapons and cure light wounds wands is huge mechanically for soloing.
3e style gestalting also works really well for having less members in your team, it shores up mechanical weaknesses and makes people more powerful by allowing them to do more types of things adding capability depth, not really adding a lot more to what a single character can do though in a single thing so not really a power spike.
Running lower level modules for a single high level character can work out really well, the lack of action economy means a lot in fight balance.
If they run two characters it gets less personal and more 3rd person perspective, my tastes run to preferring more first person single character immersion.
While NPCs can make it more like a normal party for capabilities and action economy, I find having a pet generally works better so the PC does not feel others are doing the work for them or bailing them out. An animal companion/familiar/eidolon whatever feels more like part of your character and less like a DM PC.
Doing a single person thing with no pets can be super rewarding though as it is all you. Being an actual thief doing a burglary is a lot easier to feel like a burglary for a single rogue than for a group with a paladin and a druid and a monk. As a DM you can really tune the adventure to the character and their character concept instead of to an independent story line for a group as you don't need to worry about other PCs' spotlight time or keeping the action appropriate for a whole group.
For D&D since there are generally four niches (warrior, skill person, healer, utility magic) multiclassing or hybrid classes work fairly well for a solo person even if they are weaker than a maxed out single class specialist would be. Playing a 3e wizard who dipped ranger costs a caster level and your highest level spells half the time, but those extra hp and the ability to use weapons and cure light wounds wands is huge mechanically for soloing.
3e style gestalting also works really well for having less members in your team, it shores up mechanical weaknesses and makes people more powerful by allowing them to do more types of things adding capability depth, not really adding a lot more to what a single character can do though in a single thing so not really a power spike.
Running lower level modules for a single high level character can work out really well, the lack of action economy means a lot in fight balance.
