Yeah, level 5 is definitely a big break point, level 11 much less so though IME. I have one campaign with three active PC groups, PCs can switch between groups, the highest level PC is 10th (thanks to a Comet card from Deck of Many Things) so new PCs come in at 5th level. The current level spreads by group are 6-9, 7-10, and 7-8. Those all work fine in 5e.
Groups - I have a lot of players, this is just my Faerun campaign. There are 3 Wilderlands PC groups too, but only one is running currently.
1. The Barrowmazers
1. Moxy (Claire) female Tiefling Bard 10, College of Swords
2. Mac (Matt) male Half Elf level 9 Vengeance Paladin 6/Fighter 3
3. Liam (Kermit) male Halfling Arcane Trickster Rogue 8
4. Droghall (Bill) male Kroxiger Totem Barbarian 8
5. Spartigus (Gus) male Human Champion Fighter 8
6. Aya (Judith) female Aasimar Untherite Light Cleric 8 of Shamash
7.
Petyr (Jack), male Aasimar Warlock 7
(Celestial)
8. Sir Glendor (Rich) male human Paladin 9 - currently on hiatus
2. The Faerun 7
1.
Eamon of the Yellow Rose (Bill) male Human
Monk-8 (Kensai)
2.
Greeba of Soravia (Jelena) female Half-Orc
Barbarian-8 (Berserker)
3.
Gorlock the Warlock (Tony) male Half-Elf
Warlock-8 (Celestial)
4.
Nathia Truthfist (Kimberly) female Goliath
Fighter-8 (Champion)
5.
Wisteria of Skullspire (Jelly) female Moon Elf
Cleric-7 (Grave)
6.
Joell Elderberry (Max) male Aasimar Companion of the Noble Heart
Paladin-7 (Oath of Conquest)
7.
Blurb Birchbark (Phil) male Firbolg Shepherd
Druid-7 (Circle of the Shepherd)
3.
Norrin's Band:
1. Lord Norrin (Geoff)
, Knight of Arcata, the Baron D'Ashe, Son of Thorin, Father of Teela D'Ashe Norrinsdottir. Human male
Fighter-9 (Champion) PB+3 XP
47,107/48,000
AC 24 (plate +1 & shield +2, cloak)
HP 85 (13+9/level)
P-PER 15 P-INV 12
P-INS 15 MI:
+2 longsword,
+1 plate armour,
+2 shield, cloak of protection (a). Henchman:
Rondus
2. Queale (Keelia) Half-Elf female Horizon Walker
Ranger-8 XP
42,702/48,000
AC 17 (mithril half plate)
HP 76 (13+9/level)
P-PER 16 P-INV 13 P-INS 16 MI: rabbit fur slippers of elvenkind, +1 arrows,
ethereal diadem (in pack, a), +1 longbow,
Oathbow (a),
+1 Durgeddin Rapier.
3. Meryem Bloodletter of Reghed (Roxy) Human female Berserker
Barbarian-8 XP
33,598/34,000
AC 20 (15 half plate +2 DEX +3 shield +1)
HP 85 (15+10/level)
P-PER 10 P-INV 10 P-INS 10. MI: +1 Duergar greatsword,
+3 battleaxe of Durgeddin, +1 shield. Henchman:
Hugo
4. Goltho 'Bearchaser' (Tim), Goliath male
Fighter-6 (Arcane Archer) XP
19,528/23,000
AC 18 (Glamered Half Plate +1)
HP 58 (13+9/lvl) P-PER 14 P-INV 11 P-INS 11 MI: Yew Greatbow +1, Longsword +1, Goggles of Night,
Glamered Half Plate +1
5. Kevan Blackguard (Jack) Half-Elf male
Bard-6 (Lore) XP
17,237/23,000
AC 17 (+2 studded)
HP 45 (10+7/lvl)
P-PER 14 P-INS 12 MI: JAODAR’S TOME OF ENCHANTMENT (a) (+1 to Enchantment Save DC),
Studded Leather +2, Medallion of Thoughts, +1 Shortsword, Immovable Rod, Wand of Arcane Lock Henchman:
Tod