You are typically paid the appropriate amount of the role, so assuming its an increased grade level and you aren’t top of the band (which can overlap) then you should be paid more.
I think its a great option to get some experience but its not without its risks. For instance, if your old team is restructured and your “home” role is impacted, without being there and knowing you would likely stay on in the seconded role, you probably wont keep your old role. Then if they decide not to permanently give you the seconded role you end up redundant. Depends whats happening at your work, at my work, theres restructures all over the place atm like nothing I’ve ever seen before. Normally I’d say the risk is low.
At my workplace, people management is a “hat”. I was already at the grade of the people management role when I took it on so I didn’t get any extra pay.