Doubling of barlines and time signatures

#1 is normal /correct notation - that's called a courtesy time signature, and it's required by the rules of proper music notation as without it, most people reading the score would miss the change. However, if you wish to turn it off for some special purpose (like creating exercsise sheets not meant to be read straight though), you can - globally for the whole score via Style / General or for any individual change via right click menu and/or the Inspector.

For #2, that's a known bu that will hopefully be fixed. See #18510: incorrect barlines with start repeat at beginning of system. Although so far, I think I had only seen it in cases where multimeasure rests were involved. You might want to post your score so we can see if there is something special about it triggering this problem.