D&D 5E Suggestions for a 2 player group

[Shiroiken]

I ran a two player campaign back in 1E, where they had 2 NPCs with them for several adventures, but not all the time. In general I'd focus more on the social and exploration tiers than the combat tier. Investigation adventures are far more interesting, and don't need nearly as much combat as other adventures. Enemies in combat are best if at least semi-intelligent, because they may take hostages if both PCs are dropped to 0 HP (which can happen a bit more easily with fewer players), preventing a TPK that ends the campaign. I'd choose to use milestone leveling or provide xp for non-combat challenges to ensure it doesn't take forever to level, due to the limited combat.

 

[Horwath]

I would suggest gestalt rules for these 2 players.

Every player picks 2 class for their characters.

Take better of HPs from both classes. or go with average.
Same for HDs for healing

Take better of weapon/armor proficiencies

Take all 4 saves from both classes.
If saves overlap give extra saves, but make sure that 2 are from dex,con,wis and 2 from str,int,cha group.

Take skills from both classes.

For every armor/weapon category that overlaps between classes give extra skill or tool+language proficiency.

 

[NotAYakk]

Try running everything completely normal, just treat them as lower level

2 P    Use Adventure built for party of
3      1
4      2
5      3
6      3
7      4
8      4
9      5
10     5
11     6
12     6
13     7
14     7
15     8
16     9
17     9
18     10
19     11
20     12

(this is based off the DMG encounter builder and encounter size math system, or rather math derived from it).

If the adventure expects you'll level (say, an adventure for level 1-3 characters), you may have to adjust leveling speed.