For Dylan most non-Welsh will think (wrongly) that they know how to pronounce it.
Aled, Marc, Owen, Elis, Wyn, Bryn - all straightforward pronunciation though may be mispelled
Rhodri, Huw, Hefin, Morgan, Rhys, Sion, pronunciation likely won't be quite right but may be near enough.
I like Nye (short for Aneurin)
I also like
Ifor
Ifan
Ieuan
Iestyn
Owain, Alun, LlÅ·r, Llewelyn, Tudur, Dylan, will all be mispronounced at first/by some.