I really think it's a cursed mission to chase perfectly balanced matches.
In terms of overall experience, the best approach in general is a purely random one. This is how you avoid the experience of getting trapped in a 20 game losing streak, even if you are a really good player.
If you allow the natural balance of good players winning more often and bad players losing more often, you will find things get a lot less messy in between. This also provides your bad players an opportunity to occasionally witness what they could become. When you only play someone 1% stronger than yourself, you probably don't have a great idea of what the upper bound actually feels like. This can become a serious trap for players who are seeking to grow their skills.
In terms of overall experience, the best approach in general is a purely random one. This is how you avoid the experience of getting trapped in a 20 game losing streak, even if you are a really good player.
If you allow the natural balance of good players winning more often and bad players losing more often, you will find things get a lot less messy in between. This also provides your bad players an opportunity to occasionally witness what they could become. When you only play someone 1% stronger than yourself, you probably don't have a great idea of what the upper bound actually feels like. This can become a serious trap for players who are seeking to grow their skills.