are pay slips usually required for claiming workexp and if there were no pay slips of the jobs
Yes/No!
Yes. If your former employer is not providing any references and you are writing a letter then you need this to prove how much you earned. If you do not have that and you have old bank statements showing credits from your former employer or your initial contract would help.
No. If your employer has written a detailed letter including your salary, rewards, job description, etc then you do not need this.
Will it create any problem later on .
Depends on which option you are choosing but if you can provide enough evidence and explanation you would be fine I guess.