Is it excused if the underwear is affected by a few drops of urine when using paper tissues for protection, and what kind of cloth is suitable for protection and how should it be purified?

After minute drops of urine pass through all layers of the tissues, and any doubt about this is due to excessive waswasah (whispering of Satan/obsessive thoughts), it is obligatory to disregard this and pay no attention to it. Ignoring waswasah cures it. If urinary incontinence is merely an illusion, then it should not be heeded.

However, if urine drops are actually falling despite the use of tissues for precaution, then a small amount of urinary incontinence is excused after taking full precautions, due to the difficulty of guarding against it. For Islamic law is built upon ease, not hardship, and Allah knows best.