different types of wazeefas?

[Adab]

as salaam - please excuse my ignorance in this matter, but im just curious to know how wazeefas have different effects. For example - i know that using a prescribed wazeefa without permission can have a bad effect on a person, or in some cases it will have no effect at all. but then there are some wazeefas - ( i have a kitaab of wazeefas) and in the 1st page they author gives permission to any muslim to use any of the wazeefas for a legitimate purpose. I was looking on the internet and came across many sites with wazeefas- but not controlled or made for individual needs, just general - how would the effect work? also, a person needs to have a clean niyyat and be steadfast in salaah for a wazeefa to be effective, but does the amount of namaaz you read and the intention affect how fast the wazeefa will work? can a person just read wazeefas (like those with the 99 names of Allah) from a book without permission and will it be effective if the person is sincere? - also on this website imaam has alot of wazeefas in the archives, are they there for all members to use freely or should special permission be taken for it to work? what would happen if a wazeefa was started without imaams permission would it be allowed and would it have a good effect- it i always better to consult a imam with a specific situation but im curious. and how long do wazeefas noramally take for the effect to be seen? alot of questions, but its just a general question - i will not and do not intend to use any wazeefa without permission for my individual situation, but for future reference it would be nice to know. i know of some moulanas who do the wazeefas on your behalf - is it better to do it yourself or ask a learned person to read it for you?

[Saracen]

Assalamu 'Alaykum wa Rahmatullahi wa Barakatuhu

I pray you all are in the best of health and imaan, Ameen.

Could some learned brother or sister please answer the questions asked, Jazakallah khairun