Yes. Pristine Angel is not a land creature and protectiom only stops damage, enchanting/equipping, targeting, and blocking (DEBT) - these spells do none of these.
Yes and yes. Pristine angel has protection, and that ability only does four very specific things, which you can remember by DEBT:
Can't be Damaged by X
Can't be Enchanted/Equipped/Fortified by X
Can't be Blocked by X
Can't be Targeted by X
Just because the angel is being affected does not make it a target. Ony the word "target" ever makes anything a target, either in the rules text of the card or in the rules for a keyword ability (including enchant). Neither card des anything that protection could stop.
It prevents Damage from whatever is being protected from
It makes the creature with protection unable to be Enchanted by whatever is being protected from
It makes creatures from which the creature is protected unable to Block the creature with protection
It makes the creature with protection unable to be Targeted by whatever is being protected from
The sweepers you mentioned do not damage, enchant, block, or target, so protection does nothing to stop them.
Neither Cleansing Nova nor Planar Outburst causes damage to anything (C.R. 702.16e) nor targets anything ("all creatures", "all artifacts and enchantments", and "all nonland permanents" don't identify any targets; a sorcery spell targets something only if it identifies it with the word "target" [C.R. 114.1a], or uses a keyword that does so [C.R. 114.1e; see also C.R. 114.10a; under C.R. 701.34a, the support keyword action also uses "target [something]"]) (C.R. 702.16b), so Pristine Angel's protection from artifacts and from all colors has no effect on either spell (C.R. 702.16c-d, 702.16f don't apply to either spell here). See also this thread.
EDIT (May 3, 2018): Edited to conform to rule update with Dominaria.
I̟̥͍̠ͅn̩͉̣͍̬͚ͅ ̬̬͖t̯̹̞̺͖͓̯̤h̘͍̬e͙̯͈̖̼̮ ̭̬f̺̲̲̪i͙͉̟̩̰r̪̝͚͈̝̥͍̝̲s̼̻͇̘̳͔ͅt̲̺̳̗̜̪̙ ̳̺̥̻͚̗ͅm̜̜̟̰͈͓͎͇o̝̖̮̝͇m̯̻̞̼̫̗͓̤e̩̯̬̮̩n͎̱̪̲̹͖t͇̖s̰̮ͅ,̤̲͙̻̭̻̯̹̰ ̖t̫̙̺̯͖͚̯ͅh͙̯̦̳̗̰̟e͖̪͉̼̯ ̪͕g̞̣͔a̗̦t̬̬͓͙̫̖̭̻e̩̻̯ ̜̖̦̖̤̭͙̬t̞̹̥̪͎͉ͅo͕͚͍͇̲͇͓̺ ̭̬͙͈̣̻t͈͍͙͓̫̖͙̩h̪̬̖̙e̗͈ ̗̬̟̞̺̤͉̯ͅa̦̯͚̙̜̮f͉͙̲̣̞̼t̪̤̞̣͚e̲͉̳̥r͇̪̙͚͓l̥̞̞͎̹̯̹ͅi͓̬f̮̥̬̞͈ͅe͎ ̟̩̤̳̠̯̩̯o̮̘̲p̟͚̣̞͉͓e͍̩̣n͔̼͕͚̜e̬̱d̼̘͎̖̹͍̮̠,͖̺̭̱̮ ̣̲͖̬̪̭̥a̪͚n̟̲̝̤̤̞̗d̘̱̗͇̮͕̳͕͔ ͖̞͉͎t̹̙͎h̰̱͉̗e̪̞̱̝̹̩ͅ ̠̱̩̭̦p̯̙e͓o̳͚̰̯̺̱̰͔̘p̬͎̱̣̼̩͇l̗̟̖͚̠e̱͉͔̱̦̬̟̙ ̖͚̪͔̼̦w̺̖̤̱e͖̗̻̦͓̖̘̜r̭̥e͔̹̫̱͕̦̰͕ ̗͔̠p̠̗͍͍̱̳̠r̰͔͎̰o͉̥͓̰͚̥s̟͚̹̱͔̣t͉̙̳̖͖̪̮r̥̘̥͙̹a͉̟̫̟̳̠̟̭t͈̜̰͈͎e̞̣̭̲̬ ͚̗̯̟͙i͍͖̰̘̦͖͉ṇ̮̻̯̦̲̩͍ ̦̮͚̫̤t͉͖̫͕ͅͅh͙̮̻̘̣̮̼e͕̺ ͙l͕̠͎̰̥i̲͓͉̲g̫̳̟͈͇̖h̠̦̖t͓̯͎̗ ̳̪̘̟̙̩̦o̫̲f̙͔̰̙̠ ̹̪̗͇̯t͖̼̼͉͖̬h̹͇̩e͚̖̺̤͉̹͕̪ ͚͓̭̝̺G͎̗̯̩o̫̯̮̟̮̳̘d̜̲͙̠-̩̳̯̲̗̜P̹̘̥͉̝h͍͈̗̖̝ͅa͍̗̮̼̗r̜̖͇̙̺a̭̺͔̞̳͈o̪̣͓̯̬͙̯̰̗h̖̦͈̥̯͔.͇̣̙̝
Yes and yes. Pristine angel has protection, and that ability only does four very specific things, which you can remember by DEBT:
Can't be Damaged by X
Can't be Enchanted/Equipped/Fortified by X
Can't be Blocked by X
Can't be Targeted by X
Just because the angel is being affected does not make it a target. Ony the word "target" ever makes anything a target, either in the rules text of the card or in the rules for a keyword ability (including enchant). Neither card des anything that protection could stop.
Former Rules Advisor
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(The Gamers: Dorkness Rising)
"Any sufficiently analyzed magic is indistinguishable from science."
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Planar Outburst
Pristine Angel
Yes. Protection does four things that can be encapsulated in the acronym DEBT:
It prevents Damage from whatever is being protected from
It makes the creature with protection unable to be Enchanted by whatever is being protected from
It makes creatures from which the creature is protected unable to Block the creature with protection
It makes the creature with protection unable to be Targeted by whatever is being protected from
The sweepers you mentioned do not damage, enchant, block, or target, so protection does nothing to stop them.
EDIT (May 3, 2018): Edited to conform to rule update with Dominaria.