Given that synesthesia exists, why dismiss someone perceiving things differently from other people? Some people do experience things that most people don't. They then have to come up with an explanation for it.
I have synesthenia and I perceive the world differently to other people.
Seeing spirits and ghosts is a different thing altogether though.
For me the issue of whether someone making such claims is friend / relationship material depends on a number of contextual issues.
For example, a friend from a native American tribe who grew up on rez and whose cultural and spiritual background includes a belief in spirits, or from another culture whose traditional religious beliefs included say ancestor spirits would be entirely different to a British person with no ancestral / familial history of such beliefs who claimed to see spritis / ghosts.
I do not belive in the Christian god however I would not preclude someone who does believe in that god as a friend, although I might do if they keep trying to convince me that I need to be "saved" and find Jesus.
Things that would put me off completely would be if the person
talked continually about spirits and ghosts and belief in such was central to their personal identity and created situations where this lead to them being "special" in narcisistically gratifying ways
included elements of cultural appropriation in their beliefs (e.g. native American in a past life, has native Amercian spirit guides)
included elements of invented ancient religious practices (e.g. Druidry)
included elements of cults associated with racism / white supremacy (e.g. the Steiner cult / anthroposophy, Atlantis / Lemuria, Theosophy, etc.)
has a business making money from anything to do with spirits / ghosts
has a network of powerful / influential friends, all because of their super special sprit / ghost perceiving abilities.
So really my answer is that it depends.
Anti-vaxxers who love crystal skulls, ancient aliens, the lost island of Atlantis, lizard people, etc. etc. I would run a mile
A thoughtful and apparently sane person who sees the world in a different way from others annd who is no using their ability to court money and attention from Royalty, celebrities etc. and who is modest and discreet about thier abilities, different thing altogether.