It takes about 2-3 weeks for your eyes to get used to reading horizontal scrolling. There's also some weird irregular scrolling freezes very, very rarely.. which can make it a little harder to get used to.
Also a 120hz or 144hz monitor does technically help with reading, but it won't really help much unless you're already playing 180/190BPM stuff on DT or difficult high BPM maps on HR.
Usual answer applies, just have to practice and get used to it.
Why not start with a slow song. Playing taiko doesn't mean you need to play taiko set map. (kantan/futsuu) Get used to the gameplay and you pretty much can handle the next harder diff. Some map from slow bpm easy diff go. :3 then kantan/futsuu.