Is it permissible for a Muslim to perform ablution (wudu), ritual bathing (ghusl), and prayer (salat) according to different schools of thought, and to choose the easiest of the opinions in disputed matters, in imitation of those who have permitted that?

We ask Allah to grant you a swift recovery from whispers (waswas), and we advise you to disregard them and not follow them. Your imitation (taqleed) of the Hanafi school in ablution (wudu) and the Shafi'i school in ritual bathing (ghusl) and prayer (salat) falls under the category of "talfiq" (piecing together rulings from different madhahib) on separate issues, which is not prohibited. As for always adopting the easier opinion, especially with frequent whispers, there is no harm in that, and it is not considered the blameworthy pursuit of concessions (tatabbu' al-rukhas).