The profit taking between traders and investors is different, but in principle it must have the price target. Before we buy/sell in the market, we must have a careful plan so that we can stay in the market for a long time.
Usually the terms investor and trader are different. Trader is one who regularly trades based on indicators and investors are ones who look for projects to put their money in. However in this market, both terms are often used as synonyms.
But the only plan you need is to buy at low and sell at high. You can be in the market for a long time if you place your orders with proper intuition backing them.
The market is very dynamic. No one in this world can accurately predict the direction of the market. If you are absolutely sure of the prospects of the portfolio you hold, then I don’t recommend selling everything. If you are not sure, it is best to take all profits and mix in a new portfolio that is still promising. The market will always go through a "bearish-sideways-bullish" cycle, so we need to learn to take profit/stop loss.
Your last statement does not match with the first two. When you take profit, you will have to sell - then why you recommending not selling at all? That is the stubbornness mistake that traders sometimes do in the first few months.
Creating new portfolio entries is not a good thing. The more altcoins you put in, the more risk you are carrying. Crypto should mean only bitcoin. Diversification should mean fiat markets and not altcoins. These are the only things a current generation person should look into. Anything else is bogus.