It shouldn't cause any major issues. I use a similar setup and there are two things that stand out. The color differences between monitors is usually very noticeable. I've tried my best to match my secondary to the main but it is still off enough that it is obviously different.
The second is the higher refresh rate is noticeable when moving windows across screens. But no it shouldn't cause eye strain or anything like that. The higher refresh rate just makes everything smoother when moving objects around.
ed: not sure what graphics card you will be using but there is a bug in the Nvidia drivers that gets fixed every once in a while but regresses on the next driver release. It is when using a multi-monitor setup and one of the monitors is set to 144hz the graphics card will not downclock to idle while sitting on the desktop. If power use is a concern, I recommend setting it to 120hz to avoid this issue from appearing. All assuming you are using a Nvidia graphics card. It may not even affect you if you are not using a current gen card but it is something that you may want to know.