For solo, since you play alone, there is no limitation on path. You can take as many paths as possible since no one will chase you or your ally as a team. The risk for going as many paths as possible totally depends on you. Also there are meta builds that takes 6 paths for solo mode as well.
Usually 5~6 path builds are more well-balanced than 4 path build. Then, is it better if I take 5~6 path build, like always?
It depends on the performance of the 4 path build. If you can make items fast using 4 path build and kill fast before others make all items, then use it, especially if you look for meteorite or life of tree early on, you may need 4 path builds more, especially when you need one of them for weapon crafting.
However, most builds as meta plans takes 5 paths and they perform better than 4 path builds (oppositely, 4 path build also may perform better than 5~6 path builds if it is upgraded by meteorite or tree of life). And there is auto resurrection for first 2 days and in those 2 days, you will very likely obtain all the required items if your build takes 5 paths but not 6 paths. I mean, since you have auto resurrection and time, then you might focus on stronger builds which are more likely 5 path builds. 6 path might be too late, but well-balanced 6 path builds can also out-perform 4~5 path builds. But usually this doesn't happen. Most of the builds that look its best without gold-colored rare items are made within 5 path.
From my experience in duo/squad, if your ally is a type of player who dies lot anyways in first 2 days, no matter how fast build you made and helped allies quickly using 4 path builds, your entire team will very likely lose at the end anyways (not being top 1 team). So I means you rather want to focus on your play and builds high quality by having quality equipment. Highly skilled players they all know how to survive in first 2 days without your helps.
You don't want to think too much on how many paths your builds requires as long as it takes less than or equal to 6 path. Rather, focus on the quality and performance of your build. If you use 4 path build, try to always consider getting meteorite/tree of life on early time (day 1~2), this can be risky though if you fail or getting late. Also highly well-balanced 6 path build can also outperform 4 path builds with 1 gold-colored rare item. There is no answer, so you want to focus on the quality and performance of the build rather than the number of paths.
Usually 5~6 path builds are more well-balanced than 4 path build. Then, is it better if I take 5~6 path build, like always?
It depends on the performance of the 4 path build. If you can make items fast using 4 path build and kill fast before others make all items, then use it, especially if you look for meteorite or life of tree early on, you may need 4 path builds more, especially when you need one of them for weapon crafting.
However, most builds as meta plans takes 5 paths and they perform better than 4 path builds (oppositely, 4 path build also may perform better than 5~6 path builds if it is upgraded by meteorite or tree of life). And there is auto resurrection for first 2 days and in those 2 days, you will very likely obtain all the required items if your build takes 5 paths but not 6 paths. I mean, since you have auto resurrection and time, then you might focus on stronger builds which are more likely 5 path builds. 6 path might be too late, but well-balanced 6 path builds can also out-perform 4~5 path builds. But usually this doesn't happen. Most of the builds that look its best without gold-colored rare items are made within 5 path.
From my experience in duo/squad, if your ally is a type of player who dies lot anyways in first 2 days, no matter how fast build you made and helped allies quickly using 4 path builds, your entire team will very likely lose at the end anyways (not being top 1 team). So I means you rather want to focus on your play and builds high quality by having quality equipment. Highly skilled players they all know how to survive in first 2 days without your helps.
You don't want to think too much on how many paths your builds requires as long as it takes less than or equal to 6 path. Rather, focus on the quality and performance of your build. If you use 4 path build, try to always consider getting meteorite/tree of life on early time (day 1~2), this can be risky though if you fail or getting late. Also highly well-balanced 6 path build can also outperform 4 path builds with 1 gold-colored rare item. There is no answer, so you want to focus on the quality and performance of the build rather than the number of paths.
Jotaku, Anime Game Gamer
I. Eternal Return - Korea Diamond Tier
II. Super Mecha Champions - NA Legendary Tier
III. Tokyo Ghoul: re Call to Exist - NA Top #2
IV. Strinova - Asia Gold Tier
V. Guilty Gear Strive - JP 8th Floor
VI. Onmyoji Arena - Asia Diamond Tier
VII. Fate/EXTELLA Link - NA Top #9
I. Eternal Return - Korea Diamond Tier
II. Super Mecha Champions - NA Legendary Tier
III. Tokyo Ghoul: re Call to Exist - NA Top #2
IV. Strinova - Asia Gold Tier
V. Guilty Gear Strive - JP 8th Floor
VI. Onmyoji Arena - Asia Diamond Tier
VII. Fate/EXTELLA Link - NA Top #9